We have use their background wallpaper only that is available on internet and containing their branding and logo.. ;)
you can replace it with any other image, that already many people have done with this template..

Just because something is on the internet does not make it freely available for you to use.

Tried this out and found that I can not change back to a different style once I have selected this how can I fix this issue
Had to uninstall untill then

Then you have to update your footer template, try Reverting footer template..

In my views, this is only happens when you remove their branding and claim it as yours, and we have nothing do like that,, anyway i have no extra info about this so i wont bother, its upon users to use or not..:)

Thank you that was the problem.. now have another issue will submit a new post for it...

So far awesome but I want to get rid of the white background, I want it to be transparant and change the font color how can I do this

You're still using their IP for your site which possibly earns money. Its a dangerous thing to do, I personally wouldn't take the chance.

Goto Syles & Templates Manager > Edit Stylevars > then search for "body background" and change it to your needs, and Font color option is also there

that's ridiculous..
you are over exaggerating. there is absolutely nothing wrong with using this as a background, nothing to be worried about. I have seen many such things on fan sites, different wallpapers every week. Nobody is making a profit or selling their (Marvels) brands or logos as their own.

Its a wallpaper, its a background, even though you can debate it, from where I see it he isn't doing anything dangerous, illegal or immoral with this(immoral/moral as if any such thing is yet to come out of a American/western or company). I understand what you are trying to point out here and sorry if I am being overly rude but perhaps its best you move along with that PC liberal fear mongering attitude and views of wouldn't take a non existent chance and let those who like the style use it.