Yes! it'll work as a OBW.
I like the kaleido you've got in the picture. Move your mirror around and you'll get a good idea as to what else is in store. The teal background and neutrals of the birds will make it very interesting.
As for the size of the triangles, I wouldn't go too small, in order to get a good kaleido effect going. The bigger you go, the more identifiable parts .... as you see with the loon heads around the outer edge in the reflection pictured.
Usually the size of the print determines the triangle size. It really depends on what look you like/want!
Good Luck!! I'm looking forward to following your progress on this one!