Yeah, just search the market for gde themes and install them.
To install:
menu -> control panel -> personalize appearance -> change graphical theme
This will allow you to select a theme as a whole.
Now if you find a dock bar you like but don't like the wallpaper you can change that by:
Long press on the home screen ->wallpapers ->theme wallpapers (these will be any of the wallpapers from the themes you've downloaded for gde) or wallpaper gallery (these are the original stock wallpapers) or pictures (saved pictures to your phone/sd card)
Now, on a side note if you don't like any of the wallpapers you have I did a bit of a workaround.
I also have Open Home (paid app) and downloaded a ton of themes from there. I have found that if I'm on Open Home and then switch to GDE it transfers over whatever wallpaper I had open last but it kept the GDE dock bar I had installed from whatever gde theme I had selected. Did that make sense? So basically you are not just limited to the gde wallpapers. I don't remember if the same thing happened though if I did a switch from PandaHome (free) to GDE.
edit: There is an OpenHome lite that is free and this may work too. Don't know.
I also bought the app Better Cut and this lets me use different icons on GDE. However it doesn't let you change folder icons. For folders I use abcOrganizer lite or Launcher Dock.