how to enlarge thumbnails in file upload window?

This is driving me nuts, I'm trying to update my blog from my new mac, and when I go to insert a picture, and the file upload window opens for me to select an image file, I can't adjust the size of the image thumbnail, which sucks because it's really a lot smaller than I prefer. On my windows machine, I just [control-mouse wheel] to enlarge the thumbnails, but can't find any menu options/ keystrokes/ gestures to enlarge them on my mac.

there is not a "show view options" option available as the file upload screen is a safari window and not an actual finder window, though it is laid out the same way

anyone able to help?