Here is a little something to help you out with the gallery.
https://pixeldrain.com/u/bbari9nJ
You can use https://winmerge.org/ to compare the changes I made to the scripts.
Replay Information
https://www.renpy.org/doc/html/rooms.html#replay
It works off labels so add a label for when a scene begins and "renpy.end_replay()" for when a scene ends.
Scope is used to set any variables needed for the scene.
For the gallery itself I just went with Grids and Image Buttons.
https://www.renpy.org/doc/html/screens.html?highlight=grid#grid
https://www.renpy.org/doc/html/screens.html#imagebutton
Ren'Py 7.4.6 "Lucky Dice"
https://www.renpy.org/latest.html
Edited the Main Menu a bit to get rid of the default navigation background. Added your information to the About section.