I guess with those gifs and html you are referring to your javadoc documentation. Well, my assignment says I should put it into a directory called docs/javadoc/. Take a look into your assignment, it is the safest source of wisdom for you. :-)
I guess .gif files go into code/ because they belong to "source code and related parts". Just make sure you can load your .gifs from an executable .jar as well as from the filesystem.