In Heroes of the Storm I know that I can purchase heroes with in-game gold. Is there anything else I can purchase with that gold: skins, mounts, etc.?
Currently, in game gold can be used to purchase two things:
Master Skins, which can be bought for 10,000 Gold when you have a Hero at Level 10 which is explained in the Progression System and Reward Changes blog post:
At level 10, you’ll unlock the ability to purchase a Hero’s Master Skin with Gold, which you can use to show off your prowess with that Hero in-game. Just like other Skins, a Master Skin features two variations, which you’ll have already unlocked by reaching level 10. This means that once you’ve purchased a Hero’s Master Skin, you’ll immediately be able to use its variations in-game.
and the Piggy Bank Mount which is 20,000 gold.