The Android app simply reports something "went wrong" when trying to upload an image that is too large (>2 MB). I didn't realize there was anything wrong with my image until I happened to notice the 2 MB warning in the non-mobile site's image upload page.
A more concise "Image is too large" error would help users properly respond to the problem (and likely downsize their image, reupload, and continue).
Screenshots
The top right image selected:
In progress...
The error:
Also, the limit to file uploads is apparently 2MiB, not 2MB: