You can have a photo booth, you'd have to work with the PTA a little
bit and have the photo booth during school events. When I worked for
a NPO I would draw up and paint large backdrops for Easter, Christmas,
and Valentines day and charge $3 a photo, You just need to have a
color printer and photo paper, I'd print the photos 3x5 and back them
on construction paper, put a few stickers and viola! I usually made
about $100 -$150 per event.
Artsonia also has an option where parents can buy their child's
artwork and you get a portion of the proceeds. Again it isn't a big
money maker but it may work for small supplements to your budget. See
if you can get your PTA involved, sometimes they can give you a
portion of their profits from bake sales, plant sales, bingo nights
etc. Maybe you can even do family art night, if you buys some
inexpensive craft kits ($1-2 dollars per kit) from oriental trading,
you can charge $5 a student with a parent and turn a profit from it.
Or even maybe have some kind of raffle for an art prize (an art kit,
or a portrait painting).