Maybe just start off simple.
Draw the two, and work on all their details. Don't really work on the background.
Thing is, its better to have something..even if its not what you wanted in the end.
If you have time, you should focus on the background. ^_^
I know when I first start off a picture, it looks like it is no good. And I'm tempted to stop and try and redraw or figure something else out. Yet most of the time as I continue through with it, the picture turns out better then the start looked.
My start My finish When i first started drawing this piece, it gave me a hard time and I wanted to constantly start over, or try and choose a new pose...but I kept it and just altered things as I went, fixing things up and going with it. The finished product turned out way better than what I thought it would be.
All in all just hop onto the project, focus onto it, and just keep at it.