Hello tomini and welcome to the forum 🙂
If you need changes in apps that you have not built, you can always ask the app author (us in this case) - either in the forum or via the feedback feature in r3. Please do not make changes in apps directly, as these changes are lost if you ever choose to update these apps. You can safely extend apps and overwrite forms, but this takes some experience to do - there is a documentation on how to do so safely.
Regarding your requests: I´ll have a look to increase the max. image size and preview field size. Please be aware that 128 kb is already extreme for small images. If possible you should try to downsize images to not flood your system with unnecessarily large images.