This is my one remaining 'big issue' with iOS - no way to upload in Safari.
If I want to change my forum avatar, or upload a wallpaper, for example, I have to it via the laptop.
Alternative Browsers, such as Icab and Atomic allow uploads. As do some of the PDF Reader/File managers apps (Goodreader; Readledoc). I agree that Safari should do this - it's really crazy that it doesn't. But there are several pretty easy work arounds.
It's possible, but by the time I fiddle around with stuff, it's just easier to grab my MBA or use the iMac....Apple still won't give us a decent file manager. A mild niggle I guess, I wasn't expecting it anyway. I often run my iPad alongside my Pro or my MBA anyway.