@Scannigan: I'm with @Keigan on this one.
Before you do any coding, sketch a rough layout of how you want the theme to look. You can start with simple pencil and paper to get the basic layout of elements, or use a design tool such as Photoshop, GIMP, Paint.net, Inkscape, Illustrator, etc.
Here are some simple basics. There are 4 main Views:
System
Carousel with System Logos
Basic
Gamelist
System Logo
Detailed
Gamelist
System Logo
Metadata (image, description, rating, genre, etc)
Video
Same as Detailed View, but with a Video instead of an Image
You don't need to support the Video View if you don't want to. Chances are, if other people like your theme, there will be someone out there that will add the Video support for you.
Start by working out what elements you want to show on each View.
The Basic View is pretty rigid, but you can add System specific images like controllers and consoles if you want.
The System View used to be pretty set, but now you can style the Carousel to look however you want. Check out the BaseVid theme in the Toolkit as an example. As with the Basic View, you can also add extra images to each System if you want.
With the Detailed View, you don't have to show all the metadata if you don't want to. Maybe you don't care about number of times played, or the name of the publisher. You can hide any info you don't want to show.
Now just draw some rectangles. For the Detailed View as an example, maybe you want the Gamelist on the right of the screen, so you draw a rectangle on the right of the screen. You might want a big image in the middle, so draw a big rectangle in the middle. Maybe you want the System Logo under the Gamelist, so you shorten the Gamelist a little and draw a smaller rectangle under it.
Keep going until you have a layout that you like the look of. If you are using pencil and paper, now might be the time to move to a computer program so you can get exact numbers for the <pos> and <size> poperties.