Tricopter have that special tail mechanism that makes them hard to improvise. But now with a 3d printer you can print and customise a complete machine. Here are 2 very interesting projects for this winter :
A carbon fiber folding tricopter, with carbon fibers tubes for the arms, that has all its small pieces 3d printed. What is very interesting about this tricopter is its small 250 size and that its center plates also protects the yaw mechanics.
The mini FPV Tricopter
This 250 tricopter is completely made of 3d printed parts and offers lots of room for all the junk inside. It also allows very clean build and well protected components inside.