Here's loads of fun things that you can do with graphics, all suitable for KS3 but would also keep KS4 and even KS5 kids happy too.
OLD STUFF - Fireworks, Drawplus, Flash etc..
|Chav Animals||Spot the Difference||Speed Art||Julian Opie|
|rollover buttons||drawplus animals|
New(ish) Stuff - Photopea and Paint.net (well that's it so far, give me a chance...)