Ah sweet! Nice use of blender; I'm just starting to learn to use it. I'm a long time Ubuntu user, if you need help give a holler. GL on the dist upgrade; I generally stick with LTS unless I get some sort of new/better hardware support in a tweenlease.
Talk to ya later, I'm starcannon on the ubuntuforums.org website, but I haven't been on as much as usual this last week.
Might not necessarily be more lightsources...but some of them have options for setting the type of shadows, etc. Spotlights allow you to "soften" up the spot. Area lights have an option for setting the shadow samples...more means softer and more realistic shadows..but longer render times. Hemi-lights are a more even, diffuse light source as well. You might also look into ambient occlusion...can't offer you much advice there...I am still messing around with that.