Utterly Mad

Hmm, for a good example of a creepy cartoon game, look at Knock Knock. Also, for the mirror thing, almost the EXACT thing you said was done in Doom3, and it was terrifying. Plus, if we are going Obscure Lovecraft, bring in Cythlla and Yog Sothoth. Most people are only familiar with Cthulhu, Gnarly, and Hastur. The King in Yellow would be a neat thing too, as is the Hanged King from SCP. Also, for monsters, if going Lovecraft, shy away from Shoggoths and Deep Ones. They are too familiar to most people, and the emphasis is on the bizarre and unknown in Lovecraft.