More links on that topic for you:
http://www.fencecheck.com/forums/index.php/topic,3197.0.html - tons of pics and chatter on the topic of blackbirds
http://www.airshowfan.com/blackbirdsindex.html - some more pics and quite good information about how to distinguish the different type of blackbirds
also make shure to check out http://www.airliners.net/search/ and search for “blackbird” there. (sorry, posting the result url doesn’t work)
After that, please take more care for details. Like perhaps you don’t know but the plane on the photo isn’t the usual sr-71, actually there are several types of “blackbirds”, as you can see in the second link.
You should also try to add sharp corners where they should be, like the border of the top and the bottom of the aircraft. The shape of the cockpits also needs some work. Plus if you look at the rear end of the center fuselage, it’s quite different from what you can see in the photo you posted. I’m also largely in doubt of the shape of the grillie-things on the outer wings, afics, they aren’t embossed at all, yet barely visible. And there’s still more that looks weird right now.
But don’t give up, facing all the work left to do, having your own rendered wallpaper is the most rewarding thing ever.