There are so many horror games with blood meaning that it is fine. But do not push it. There was one time where there was a game that blood would like spurt out after hitting somebody. They either had to change the game so there was less blood or it got taken down. Blood is perfectly fine in roblox as long as your not dedicating your game to have as much blood as possible.
And, you can also add an important notification for the xbox player to turn off blood & gore, make sure there is a settings tab at the main menu.
In my opinion, it looks like you went a little overboard, and just as @Ty_IsHomeSchooled said, it looks like about 100 people exploded in there, I think if you took the majority of the blood off the walls, and only add a little bit of blood around the zombie, you should be fine. You just wont be able to put it on Xbox just as @GamersInternational also said.
Well, its ok based on the picture right there. If too much blood spread around, then, as what @RecBtw said, make sure to put a warning or a disclamier, that’s the first important thing you need to do.
Truthfully speaking, Roblox is rated as Everyone 10+ from the ESRB, so be prepared
Thanks, Viro