Skins, I can do. I've installed a few before, but stuck with this one as I didn't much like the other ones. I may still have the basic one installed.
: Yes, in fact, the subSilver (i.e., the phpBB default) style is still installed. Click on the profile link at the top, and scroll down -- near where you set your time-zone and all of that, there should be a drop-down entitled "Board Style." The current one is Dark Sky, and subSilver is the brighter default theme. Let me know if it doesn't show up, I've just enabled users to change the style.