What do you think my staffie is crossed with?

Really does appear to be quite large, could be some dane, or maybe some mastiff in there, possibly greyhound, but her head is so blocky. I agree with the other poster though, often with mixed breeds, the dog may resemble something different. I saw pictures of a cocker x basenji litter and there were some that looked like one or the other breed, and others looking like neither breed.