Using this method posted by justinsimison:
The ONLY changes required are:
HKEY_LOCAL_MACHINE\Software\Samsung\MMS\Settings
Change "UAProf" value to: http://uaprof.vtext.com/utstar/xv68k/xv68k.xml
Change "UserAgent" value to: utstar68kv1
I can now get picture messages in bigger form. The largest I have gotten yet was one at 137K at 1600 x 1200 pixels. This is MUCH better than the original 22K files I used to get.
Just now I sent myself a picture and it came in at 96K.
Can anyone CAB up this REG edit for easy install for other people?