Quick Terminal tip:
Make a copy of the /Library/Desktop Pictures/Solid Colors/ directory in your home folder and delete all dark and medium gray color files from the copy.
In “Terminal” > “Preferences” > “Profiles” choose the “Basic” profile. Drag your copy of the Solid Colors folder from the Finder on to area next to the “Image” label where it says “no Background Image”.
If you already have Terminal windows using this profile they should apply the color immediately, and any other terminal window you open will get a random background from the colors in your folder.
If you prefer light text on dark background you can remove the lighter colors from the folder instead, or make your own set of background images. Enjoy!