The problem with the data upload limit for attachments has been fixed. I have restored it to 30MegaBytes. A recent forum software upgrade was responsible for the changed limit. Please accept my apologies for missing this when upgrading the forum sofware, Mabula.
Corrupted image files
Can you elaborate a bit on the images? What type are they (FITS, CR2, other format)? How were they obtained (RAW images, processed in other apps)? What other app(s) do they open in? Can you post an example? I am afraid it is impossible to say anything sensible without more info...