Hm, you know what? You don't have to give the pictures titles but it would be nice to acknowledge which characters you're portraying and any images you used to reference them, especially if (and this is an if) you copied or traced in any way. For example, the Iron Man and Garfield are very recognisable and you've written the names on the paper itself for some of them, but it's also good to be thorough with every known reference you make.