From The Document Foundation Wiki
- Firstly, insert a picture control in the form.
- Then set the dimensions of the picture control so that the size is big enough for the largest of the pictures you want to display.
- Choose the background colour to be the same as the colour of the form, for example white on white, and with no frame.
- Finally, to avoid possible distortion of the images and to allow them to display in their original size, set scale to No.