Have you checked out the GUI Champs?  http://www.guichamps.com/gallery

Therre are some good ones there.

That darned widget again! Sole my reply. Zubaz  AND Tiggs

boy, did you time it perfectly.....

follow the link to plenty of Plastic Fantastic accessories......
(links have been acting up recently, may have to copy/paste to a new browser page)

http://www.wincustomize.com/skins.aspx?search=Plastic%20Fantastic

there are some screenies there also to get some ideas from....

Vlad has some excellent walls kids would love as well.....lower resolution ones are free....

http://www.vladstudio.com/wallpapers/

if you're using XP bootskins...there is a koala pirate and Bart Simpson boot...

http://sydneysiders.wincustomize.com/skins.aspx?skinid=10032&libid=32

http://sydneysiders.wincustomize.com/skins.aspx?skinid=10043&libid=32

and some bright & colourful simple scenes...

http://sydneysiders.wincustomize.com/skins.aspx?skinid=10107&libid=32

http://sydneysiders.wincustomize.com/skins.aspx?skinid=10037&libid=32

http://sydneysiders.wincustomize.com/skins.aspx?skinid=9974&libid=32

http://sydneysiders.wincustomize.com/skins.aspx?skinid=9968&libid=32

and lastly...this site has some lovely Disney kids wallpapers and others....

http://www.wallpapervillage.com/category.php?pagenum=0&catid=28

Edit..

yes, you will have to copy/paste into new browser....seems all links are up the creek....  *sigh*...