Filesize issues.
Using Jamroom
Probably because the valid image sizes for display via the image system are:
image size - must be one of: xxsmall,xsmall,56,small,icon96,icon,medium,large,larger,xlarge,xxlarge,xxxlarge,1280,originalSo since the images are being re-processed excessively large files would take up more space on the server.
I've got a tracker open on adding extra sizes.
eg, one of them is: