Screens, Wallpapers, etc...

Wallpapers

Screenshots

Characters

Excellent idea. That is a really really nice background. Promotional material is a great thing to create and well help tons with marketing and pre-launch. Create as much of this kind of stuff as you can.
Keep up the excellent work.

I think instead of constantly making new posts I am just going to update the first post when I have new images to put out. Seems like it would be more efficient and orderly.

Yup. Absolutely, only use a new post for a new type of graphics, if you make like forum avatars, or like signature banners, etc. Each thread is like a category. Some games will likely have more graphical stuff then others, but I figured if each game has the same sections, it makes stuff more stream lined. You can also post concept art pages, screenshots or many other stuff graphic wise you wish to share with others.
Stuff like this is awesome because it is perfect for players to take away and remember your game. Also helps fill out your social networking sites when the time comes. The theory is that when it comes time to advertise the more organized stuff is here the easier I can grab it and post it somewhere. Only separate if you have lots. If you make tons of backgrounds and screenshots, it will become hard to tell which you intend to be which, to me only the top left looks like a background the rest look like screenshots.
Keep up the good work!

You got it. Plus all screenshots will be 640X480. Any wallpapers will always be much larger.