This has happened to me a lot the first few days, and the only working way to be protected is to use imageshack cause you can easily remove your images and it does not resize unlike photobucket & it includes the Imageshack Uploader which saves you a lot of time.

I. Go First?
When you sell your backgrounds, I always went first in giving links but you can decide to make them pay first, it’s your preference.
Downside; If they decide to ban you and not pay, you run straight to your imageshack account and delete the image, it’ll stop showing in 5-30 minutes.
I remember having Rapid try that shit on me and when I removed the image he cried saying “You never said I had to pay you…” as if it wasn’t obvious enough that you’re paying when you buy a background. 

II. They Re-Uploaded!!!!
Don’t worry, every image uploader has a report feature, just provide proof of you being content owner and ask them nicely to remove it for you.
Report Imageshack
Report Photobucket
Report Tinypic I used to think Tinypic was untouchable but lately I’ve been getting some very positive response from the Tinypic Staff, so you can report there aswell now.
I’ve gotten many of my imageshack photos taken down, including Lightshot/Prntscr ones 
You do not have to worry about them re-uploading anywhere else because xat is extremely strict about their image providers, they only allow Tinypic, Photobucket and Imageshack so if you have those controlled then you should be fine.

III. They want a Re-Upload
So they tried to scam you and wants it back now that it’s deleted? Charge that bitch double, seems about right.