You can use it to store pictures and files that you want to share with other users, instead of using image upload services or crappy long count down download website.
learn PHP little by little if you don't know yet.
Try making a shoutbox to train yourself with database. (it's one of the first thing you create with mysql)
I agree with Cyan, that's one of the things I do with my website. I just store my pictures and files there, so I can use them here, and everywhere else on the web.
I use my site (mainly written in PHP) for my software, games and patches, with a lot of information. If you have anything to share yourself, you could best do that at your website.