I've always wanted to see a computer that was basically hidden organically. I love Bonsai trees, so if someone could do this, you're amazing. You could either use real or fake bonsai, obviously real is cooler but the fact that its alive and needs water and light is something to consider.
I'm thinking something a little like this stand, although not so high would work well:
Most of the components could be placed in the stand/vase structure. I'm not sure about the monitor part, but I'm thinking if it could be in the tree that would be pretty neat too.
The fake bonsais I saw were around $65-100, and 2 to 3 feet tall I think. Fake Bonsai pics: