Banner in the foreground isn't a valid image

i have a problem with the banner in the foreground.

I have uploaded this:

http://ift.tt/1wpJ0RT

The Playstore says this: "You must correct the banner in the foreground. Is not a valid image." Can you help me?

We have done it in PNG, JPEG with size 1024 x 500

I don't know where is the problem! :(