I don't think horse racing, just as a general concept, is something you'll have an easy time selling. Personally I would not even play a free game about horse racing unless it had something -really- special in terms of gameplay... just rolling dice is not enough. In this game it also seems like there's no way for the player to influence the game or to interact with opponents, in which case it might as well be a slot machine.
The cover image is silly, but the background being your decapitated head logo makes no sense at all for the style of the game. Just having a logo like that is going to put off anyone looking for family-friendly content. You also tagged the game with "Animals"... yeah, probably not going to get many fans out of that tag, if you catch my meaning?