thank you @mitu!
@aphyx have you had a chance to read through the instructions I wrote up here? https://github.com/anthonycaccese/art-book-next-es?tab=readme-ov-file#theme-customizations
a few initial things to check...
as mitu called out try to make sure the "theme" value is what you are using to name your files. For example if you are looking to create a custom image for the super nintendo, the theme value is "snes" so you would name your file snes.ext (where ext is the actualy extension for the image type you are creating)
on batocera make sure the "distribution" setting in theme configuration is set to "batocera"
make sure your files are stored in the location where I set it to look for custom images on batocera... the root folder is userdata/theme-customizations/art-book-next/
then make sure inside that folder that your images are stored in the expected sub folder... if you are creating custom backgrounds they will go in a subfolder called backgrounds. If you are creating custom logos they will go in a subfolder called logos
Please let me know if you have any questions on the readme linked earlier. Also, if you can outline what you have tried already that will be a big help.
Thank you for your kind words and hope I can help.