I think that I've got about 400+ that I've created. I haven't been able to do that since the good computer crashed. I really miss it too. It used to be a nice escape, and a good creative outlet as well. The only thing this computer has is a really primative version of Paint, so I can't do much with it.
I actually got to add some to several different sites today, but I had to go to the library to do that. This computer won't let me add images (besides icons to my profile) to Fanpop, as well as a bunch of other things I'd like to do. I pretty much spent 2 hours fanning people, adding some images, and rating a few things today.

I hate to do that

IDK how 2 do it

Yeah. It's fun.

i usually just get them from the internet or Myxer

I love to make them! They can be time consuming but they're fun to make. I can't make them all the time because I get busy but whenever I have some free time I spend it making them :).

It must have been a long time since I looked at this, as I've had to change the answer to this too.
As of Sept. 2013, there are now roughly 1,200 different wallpapers that I've created and added to assorted fanpop clubs. During that time, I've pretty much gotten the hang of using the Paint program. I was surprised to learn how much can be done with it. Sometimes I'll use Picasa in addition to it, but not always.