Use Custom Background on Irix
First you must enable 24-bit support on your X server.
Next obtain some backgrounds; depending on your display configuration most likely 1280x1024 or 1024x768 8-bit X11 PixMap (XPM) format. You can convert JPEG images to XPM using ImageView, xv, NetPBM or similar, and resizing/cropping to the correct size and aspect can be accomplished with an image editor (such as GIMP or Photoshop).
Once you have a suitable XPM file you'll need to configure 4Dwm to use it as a background. First, create and edit a .backgrounds file by copying the system.backgrounds file from /usr/lib/X11 to your home directory as .backgrounds:
cp /usr/lib/X11/system.backgrounds ~/.backgrounds
Using a text editor, add additional entries for your new backgrounds file like this:
background "Anime" command "-xpm /usr/people/neko/backgrounds/anime.xpm" default "-xpm /usr/people/neko/backgrounds/anime.xpm" readok "/usr/people/neko/backgrounds/anime.xpm"
Change the three path entries /usr/people/neko/backgrounds/anime.xpm to reflect the full name and path of the background file you are using. Also be sure to change the background name from "Anime" to whatever you'd like to show up in your Background control panel. You can add several entries like the above to easily switch between multiple backgrounds; I have at least twenty myself.
Once all this has been accomplished you can select your new background(s) from Toolchest -> Desktop -> Customize -> Background. In addition to the increased performance, you'll even get a snippet of the new background in your Desks Overview which is another benefit of using XPM files.