Here's another little trick for maximizing screen space in thumbnail view. Instead of spending a lot of time with the slider trying to get thumbnail sizes just the right size to fit the screen, try pressing Ctrl with the + and - keys. Pressing the Ctrl + (plus) will increase the thumbnails to the next best size to fit the screen and pressing Ctrl - (minus) will decrease thumbnails to the next best size to fit the screen. (For some reason this only works using the top row plus and minus keys, not the ones on the numeric keypad.)
And if you really want to maximize screen space for thumbnails, uncheck the "Details" box at the bottom of the screen. You can toggle this on and off with the shortcut Ctrl-D.

