I actually kind of think that the piece would be better if you just blended the picture on the sides, and 86ed the picture in the middle. It's easier to create a good looking blend when the pictures already have the same type of background and color effects. It'll save you time from hasseling around trying to get things to look right.
But, that is just me.
The texture idea would be one of the things that I would've first reccomended. Textures can add depth and enhancement to a piece. I would also say, just play around with the coloring of the pictures. I am not sure what program you are using, but if you're using Photoshop, try messing around with the selective coloring. It is, to me at least, a lot of fun in enhancing colors and making just certain things 'pop-out' from the graphic.
For textures, though, all you have to do is find the right one. I get a lot of my textures from
http://dearest.livejournal.com . The stuff there is AMAZING. Love that place. Pretty much, just place the texture in there and try setting the texture to different layer modes, i.e. Screen, Multiply, Soft Light etc. Each texture and layer mode are different so pretty much it's just trying to find a happy medium as to what you think looks good.
And OMFG I will now stop writing since I have literally just typed you up an essay about this. Heh. Sorry. =/