Wiki: New Category Question

[Cassandra LeMay]

Is there any easy-to-follow, step-by-step tutorial how I might best go about creating a new (sub)category that I intend primarily to classify images for a certain game? (When answering this question, please take into account that I am a complete noob when it comes to the workings of the wiki. I have used it only for uploading images so far and know how to categorize an image during the upload with pre-existing categories, but that is about the extend of my wiki knowledge.)

To provide some background to the question: I am about to start a system game and I know I will be uploading several images to the Elluiki for it. I think it would be convenient if I could have a "my system game" category for those image in addition to the usual characters, clothing, maps, and so on, some place where all the images for that game are collected, regardless if they are maps, character portraits, or whatnot. So I guess what I am looking for is a sub-page (or sub-category?) under "Games" that I can use as a category when uploading images to the Elluiki(?). How do I go about that?

Many thanks in advance for all answers.  :-)