Absolutely you can! Most artist alleys allow you to sell anything you made yourself, although some restrict it to original art pieces or prints, so check the rules before you buy a table.
In fact, at some shows it seems that art and prints are in the minority! People sell all sorts of crafts: Knitted items: hats, scarves, mittens, Pocky cozies, whatever you can think of. Sewn items: costume pieces, hats with ears on them, stuffed animals, and things like that. Do you enjoy designing and building things? Manga and anime are full of characters with oversized swords and other weapons. I’ve seen some nifty stuff built of foam and rattan and duct tape sold at cons. Keychains made out of Shrinky Dinks, by laminating small prints, or by putting small prints into acrylic keychain blanks, are easy and popular, especially because they’re inexpensive. Stickers are also a possibility, as are jewelry, bookmarks, stationery, phone charms, note cards, and anything you can think up.
Take a walk down the scrapbooking and jewelry aisles at a craft store and see if that sparks any ideas for you.
Self-published doujinshi, comics, and manga are also sold in artist alleys. And how to make and print those is a completely different tutorial, so I won’t go into that here. It’s more difficult to sell original material than fanstuff, but if you work hard at it, you can sell a decent amount.