Customising the Terminal
There are some predefined colour schemes, such as the popular green on black, or you can make your own. It is also possible to set an image as the background, and choose the transparency of the window.
It is also possible to create colour schemes using different methods, such as the one outlined in this Macworld Article.
To set a colour scheme as the default, click the button at the bottom of the Terminal Inspector.
But what if you want multiple colour schemes, or you want to send one to someone else? Luckily you can save these settings simply by saving the terminal window.
Choose all your colours and settings as above, then click the File menu and choose Save As. Navigate to Library/Application Support/Terminal. If you don't have a Terminal folder in Application Support, create one. Save the file here with a name like "colour-scheme1.term".
Now, a Terminal window with the saved settings can be opened by choosing File --> Library --> colour-scheme1. To save one of these files as the default, go to the Terminal preferences and select "Open a saved .term file when Terminal starts" then select your chosen file.
Here are a few ready made colour schemes for you to download.
As an extra quirk, you can make Terminal choose a random colour scheme using a handy applescript created by Daniel Jalkut. It can create some pretty horrible combinations, but it does contain and algorithm to make sure the contrast of the text on the background is high enough.