It occurs to me that it may be an artifact of the resolution of the display. you've got a 800x480 display, and MMS pictures are only a small fraction of that (I want to say 160xsomething, but even if it is 320x240, that's going to be 1/4 of your screen size (1/2 of each dimension)(the 160xwhatever may be video...)). Videos are going to be even worse.
Having said that, of course, it's not really much of an excuse, since there's no reason that they couldn't scale the image up, however, you'd lose a lot of the apparent resolution doing so. how much? depends on the scaling routine. You should, however, be able to extract & save the picture onto your phone, and then open the picture viewer. I am guessing, since I don't have one, but at l... (continues)