Transparent View option in 3D View?

Is there any way to view things as partially transparent in the 3D view?

I use wireframe for modelling based on a background image, but when it comes to aligning textures, I end up having to do a lot of flipping back and forth between layers, to see the background image, because textures don’t display on objects in wireframe mode.

A way to make objects partially transparent so I could see the background image, and the object at the same time, on top of each other, would be nice. Is there such a thing?

you could have two windows, one in solid and the other in wireframe, both with the background image.