If you want to have an elephant with six legs and wings, then you can do it. The problem is that people have pigeonholed fantasy into this sword and sorcery subject matter and rarely veer from that. Most stories involve a dragon, sword fighting, sorcery and an old wise wizard. Let me tell you a little something about fantasy publishers, they're tired of the same old thing.
It's incredibly rare for a publisher consider a story that is so similar to everything that has come before. There is a reason why these are classics and have been emulated over and over again. If you want to get your stuff published, then don't be afraid to break some of the commonly held rules. It doesn't have to be big.
Instead of the wise old wizard have the precocious young prodigy that has the same powers as the old men, but the temperament of a child. You can take out the dragon and replace with some other lesser known creature. What it comes down to is that if you want to be a success as a fantasy writer, then you need to shake it up a bit.
If not, then you'll need to craft a story that is so compelling that it can overcome the stagnancy of the genre.