I am not aware of other ways to do gradient.
Importing a graphic file works fine, I recomment .png files.
Just a quick caution. Gradients images tend to weigh in heavier than solid-color images. If you're looking to make your entire background a gradient, some users (especially those accessing the database via wireless) may experience a short lag the first time they go to each layout each day.
If you have a small number of layouts, this isn't such a big issue. If your users will access dozens of unique layouts on a given day, those lags may begin to bother them.
That said, I like the eye candy of gradients, too. ;)