As to why the Forum is funky about photos - name of the image, size of the image, quantity of the image:
It's not the Forum 's software other than it doesn't like YOU, No13. it's something personal by the machine.
Okay, not really. Don't cry
Seriously, the software is a generic bit of freeware and was set up by the SMF people, not me or Jon Amo or Bob Clancy. They decided how to fashion it. I suppose some actual answers to your questions are - by limiting the quantity and size of files they manage to keep post file size under some control - to help keep the loading speed under control. As for making you name each file something that the forum software hasn't seen before (such as "img0035.jpg") - It's to make things a little less cornfusing for said software.
There are sorta easy ways to work around the Forum's restrictions. Whatcha do is use one of the photo-sharing sites -- Photobucket or Flickr and so on. Basic service from them is free and with 'em you're able to put up dozens of photos per post, comment more easily on the photos, and much more. I've got a nice, long, (supposedly) easy to read and use set of instructions for Photobucket. That's what I use for this site. I've got the big file subscription -- yearly fee is $25 and I'm all of half full of my allotment. . .and I've got one heck of a lot of pictures stored there. Some folks say that an inherent risk in using one of those sites is that all of your stuff will disappear in a cloud of smoke if that site should disappear -- but if you're worried about that happening - save copies of the photos and stuff on your own hard drive/remote hard drive. Whether that'll last longer than Photobucket is another question, but don't worry too much.
I expect others will chime in with comments, but in the meantime - sorry that the way it works isn't super-easy. Deal with it!