There's not much more to it than that - you can set the size and color of the "Search for" text which appears next to the search box; you can even turn it off, which is what I did. You can also control how many results to display on the page, what languages to search in, and whether to search keywords, images, newsgroups, or Mac sites.
You can also switch which type of data to search for without opening the prefs panel -- just hit command-K for keywords, -I for images, -G for groups, and -M for Mac sites before you hit return in the search box.

