Как отображать формы на картинке в PyQt5?

Попробуйте так:

import sys
from PyQt5.QtWidgets import QWidget, QPushButton, QLabel, QHBoxLayout, \
    QVBoxLayout, QLineEdit, QFormLayout, QGroupBox, QRadioButton, \
    QMainWindow, QWidget, QGridLayout, QApplication, QSizePolicy
from PyQt5.QtCore import Qt, QSize
from PyQt5.QtGui import QFont, QPainter, QColor, QPixmap, QIcon

WINDOW_HEIGHT = 600
WINDOW_WIDTH = 600
WINDOW_NAME = 'Истребитель уток'
WINDOW_ICON_NAME = 'Images\\main_logo.png'
#WINDOW_ICON_NAME = 'Ok.png'

MAIN_FONT = 'Times'
FONT_HEADER_SIZE = 13
FONT_BODY_SIZE = 8


class FormBuilder(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.create_all_forms()
        self.fill_forms()
        self.create_layers()

    def create_all_forms(self):
        self.task_label = QLabel()

        self.control_label = QLabel()
        self.start_button = QPushButton()
        self.quit_button = QPushButton()

        self.mode_label = QLabel()
        self.first_rbutton = QRadioButton()
        self.second_rbutton = QRadioButton()
        self.third_rbutton = QRadioButton()

        self.results_label = QLabel()
        self.play_time_qedit = QLineEdit(placeholderText="Время игры")
        self.play_attempts_qedit = QLineEdit(placeholderText="Число попыток")

        self.background_image_label = QLabel()
        background_image = QPixmap("backimage.png")
        self.background_image_label.setPixmap(background_image)

    def fill_forms(self):
        self.task_label.setText("Задача: убейте всех уток за установленное время.")
        self.task_label.setFont(QFont(MAIN_FONT, FONT_HEADER_SIZE))
        self.task_label.setAlignment(Qt.AlignCenter)

        self.control_label.setText("Управление")
        self.start_button.setText("Начать игру")
        self.quit_button.setText("Закончить игру")

        self.mode_label.setText("Режим:")
        self.mode_label.setFont(QFont(MAIN_FONT, FONT_HEADER_SIZE))
        self.first_rbutton.setText("1-я скорость")
        self.first_rbutton.setChecked(True)
        self.second_rbutton.setText("2-я скорость")
        self.third_rbutton.setText("3-я скорость")

        self.results_label.setText("Результаты:")
        self.results_label.setFont(QFont(MAIN_FONT, FONT_HEADER_SIZE))
        self.play_time_qedit.setDisabled(True)
        self.play_attempts_qedit.setDisabled(True)

    def create_layers(self):
        outline = '''
            QGroupBox {
                margin-top: 2ex;
            }
            QGroupBox::title {
                subcontrol-origin: margin;
                left: 3ex;
            }
        '''

        main_layout = QVBoxLayout(self)

        task_layout = QHBoxLayout()
        task_layout.addWidget(self.task_label)
        main_layout.addLayout(task_layout)

        self.control_groupbox = QGroupBox(self.control_label.text())
        self.control_groupbox.setStyleSheet(outline)
        control_groupbox_layout = QHBoxLayout(self.control_groupbox)
        control_groupbox_layout.addWidget(self.start_button)
        control_groupbox_layout.addWidget(self.quit_button)
        main_layout.addWidget(self.control_groupbox)

        self.mode_groupbox = QGroupBox(self.mode_label.text())
        self.mode_groupbox.setStyleSheet(outline)
        mode_groupbox_layout = QHBoxLayout(self.mode_groupbox)
        mode_groupbox_layout.addWidget(self.first_rbutton)
        mode_groupbox_layout.addWidget(self.second_rbutton)
        mode_groupbox_layout.addWidget(self.third_rbutton)
        main_layout.addWidget(self.mode_groupbox)

        self.result_groupbox = QGroupBox(self.results_label.text())
        self.result_groupbox.setStyleSheet(outline)
        result_groupbox_layout = QHBoxLayout(self.result_groupbox)
        result_groupbox_layout.addWidget(self.play_time_qedit)
        result_groupbox_layout.addWidget(self.play_attempts_qedit)
        main_layout.addWidget(self.result_groupbox)

        background_image_layout = QHBoxLayout()
        background_image_layout.addWidget(self.background_image_label)
        main_layout.addLayout(background_image_layout)


class Label(QLabel):
    def __init__(self, path, w, h):
        super().__init__()
        self.setPixmap(QPixmap(path).scaled(w, h))


class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.centralWidget = QWidget()
        self.setCentralWidget(self.centralWidget)
        self.build_skeleton_with_basic_settings()
        self.create_and_connect_grid()
        
# +++ vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv   
        self.my_widget = QWidget(self.form_builder_object.background_image_label)
        self.my_widget.setFixedWidth(self.size().width()-30)

        self.layout_left = QHBoxLayout()
        for i in range(2):
            label = Label("bullet.png", 10, 40) 
            self.layout_left.addWidget(label) 
        self.layout_left.addStretch(1)
        
        self.layout_center = QHBoxLayout() 
        self.layout_center.addStretch(1)
        self.button = QPushButton() 
        self.button.setFixedWidth(25)
        self.button.setIcon(QIcon("down.png"))
        self.button.setIconSize(QSize(20, 20))
        self.layout_center.addWidget(self.button)
        self.layout_center.addStretch(1)
        
        self.layout_right = QHBoxLayout()
        self.layout_right.addStretch(1)
        for i in range(2):
            label = Label("heart_.png", 30, 30) 
            self.layout_right.addWidget(label) 
            
        my_layout = QHBoxLayout(self.my_widget)      
        my_layout.addLayout(self.layout_left, 0)
        my_layout.addLayout(self.layout_center, 1)
        my_layout.addLayout(self.layout_right, 0)
        
        
        label = Label("bullet.png", 10, 40) 
        self.layout_left.insertWidget(0, label)
        
        label = Label("heart_.png", 30, 30) 
        self.layout_right.addWidget(label) 
# +++ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    def build_skeleton_with_basic_settings(self):
        self.setFixedSize(WINDOW_WIDTH, WINDOW_HEIGHT)
        self.setWindowTitle(WINDOW_NAME)
        self.setWindowIcon(QIcon(WINDOW_ICON_NAME))

    def create_and_connect_grid(self):
        self.main_grid = QGridLayout(self.centralWidget)
        self.form_builder_object = FormBuilder()                               # + self.
        self.main_grid.addWidget(self.form_builder_object, 0, 0, Qt.AlignTop)  # + self. 


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = MainWindow()
    ex.show()
    sys.exit(app.exec_())