Well, it's been a while since I've written a critique. I don't view myself as someone who's qualified to go around critiquing, but I know how frustrating it is to request critiques and not get any, so I figured I should help out.
Anyway, let me start off by saying I like this piece. A lot. Hell, I guess you could say I love it. It's simple, concise, striking, and just plain well composed. It edges on both minimalism and surrealism, which is cool. Something I really appreciate is the use of the textured background, as it adds enough flair to not be plain while still letting the foreground objects shine out. And of course the colors on the impossible triangle are just stupendous in both choice and blending.
Okay now here's the part no one likes: what you could do better. First off, this might just be a personal style choice, but I'm not really digging the sort of gradient shading you did. On it's own I think it would look okay, but in the context of the piece I just don't think it fits. I feel like because of the hard blending on the triangle, you should have done hard shading on the hands and torso. But! that's just me. If you like what you did there, then that's perfectly fine too. The other big issue (and really it's not *that* big) is the hands, namely the index fingers and thumb. They are done well enough, but could use a lot of general improvements. The top joint on the index fingers is bent weirdly (unless this guy's double jointed like me :b) and the knuckle on the thumb is a little bulbous. The other three fingers are technically passable, but still look a little stiff. And again if it's a stylistic choice... well, it's still partially distracting, but if you're okay with it, that's all that matters. Just do some hand studies and you'll be in the clear.
Overall, excellent piece. One of your finest, I'd say. Maybe I'll get a print or something.