Okay I'm not too good @ this either.
Here's what I suggest.
IF you use photoshop.
Make a new layer.
Paste
Depending on your w/e your putting on the bg
set the hue and saturation to match it.
its nice to put it sideways cause you don't want to stretch it out too much.
blur it a bit.
make the render blur into the bg a bit
make it so that you didn't just slap on a bg.
and that should work.
(I'm not sure, but thats what I do sometimes, the outcome isn't too great, but it still works)