I'm using slackware 12.2 with icewm as my gui (Slackbuild).
Everything works wonderfully, but I find that when I set a background in ~/.icewm/preferences as such:
...
#Some Comments
DesktopBackgroundScaled=1 # 0/1
...
#Some Comments
DesktopBackgroundImage="/path/to/pic.png"
...

the background always maintains it's original aspect ratio. This means that unless I find a pic with the exact aspect ratio of my screen (I don't even know what it is or how I would calculate it) I end up with borders around the top and bottom or on the sides of the image.

Is there an alternative lightweight and independent background app that you would recommend to launch in .xinitrc that would scale the image to a true fullscreen? Or are there any parameters I can set in the preferences that will tell icewmbg to force an aspect ratio?

Also, how would I find my aspect ratio. I have a 22 inch monitor at 1680x1050 resolution.

I believe 'feh' is another option for a background image program. I've used it with fluxbox before because it allows for transparency. It has more features ... possible the ones you want.
http://linuxbrit.co.uk/feh/

look into hsetroot instead of feh. feh is a full-blown image display app whereas hsetroot was ment to set root wallpapers. feh works well if you also need a program to view images, but lacks many options hsetroot comes with.