No problem! I actually like doing stuff like that ^-^. A couple months ago I learned how to do basic photo enhancement and color correction with GIMP . It was fun to learn, and the best part is my friend was in Germany all last year, and when I asked, he offered me hundreds of non-professional grade photos for me to enhance :D. I practiced enhancing hundreds of photos and I even tried doing some fake GIMP HDR thingies on some of them with nice effects :). It was made even better because most of the photos were actually taken in excellent locations under excellent conditions but with bad settings. So I was able to bring out a lot of color from his stuff. As a result of all that work, I'm at least fairly good at spotting unnatural/improper colors in photo-like images, and I have practice trying to correct them. Spotting unnatural colors comes from all the pictures I over-corrected before I got used to the fact that the real world doesn't have 100% saturated colors everywhere like the anime world does >.>.

I'm no pro, but I like doing this kind of stuff for fun, so your background was a good challenge for me to try ^^.

Also, forgot to tell you what I did exactly xP so you can maybe use some of it:

1) The brick wall was a little bright (and so is CC) so I moved up the tail end of the levels to make things more balanced.

2) CC was in general way too saturated so I dropped a little saturation off every color

3) Then I targeted green and yellow and desaturated those (also turned brightness down a tad) a lot until the green/yellow looked more natural

4) Due to the desaturation of the green, CC looked a little odd on the strong red of the wall (red became stronger after step 1) so I desaturated the red a bit too

5) CC was well overlayed and picked up the texture of the wall, but she could use a little noise to make her blend better so I added noise to the whole image (this is where the texture got out of control)

6) I would've also wanted to blur the edges of most of the overlayed images a bit to make the transition less sharp