A program to generate a scene in POV-Ray makes a great assignment. I assigned a castle. A sub makes a brick, another sub makes a wall, etc. Use a little trig to make a turret. You could also say that the brick should look like a Lego. The students can build what they draw if they want.

This assignment generates an artifact that doesn't require a computer to see it. You can print it out, and it actually looks like something.