I did a quick Google search using various phrases relating to what we discussed at this evening's general meeting and found at least one nice "text editor" type rename utility - Oscar's File Renamer. This works exactly as you described...BUT, it doesn't display image thumbnails, so that's useless for your image renaming purposes.
However, booting up my Windows XP Pro VM to have a look at what was nagging me about my comment that I've seen a file browser where you could click right on the name, rename the file, and click on the next, etc., guess what? What was nagging me was I could swear this was Windows native behavior! I kept telling myself that with all the Windows users at the meeting someone would nave noted that, but there's nothing like trying something to see.
Well...that is Windows native behavior! I accessed a folder of files on my host OS using the XP file manager, clicked an image file thumbnail to select it, clicked again in the file name box and changed the name. Moving on to the next one didn't even require an Enter to accept the previous edit. Maybe you never stumbled upon this behavior/functionality.
So, either this, or simply navigating along with the down-arrow key, pressing F2 to edit the name, and down-arrowing to the next file will do just what you wanted to do. It's not as cool as that extended live-edit with commit at the end that Oscar gives you, but it's free, in place, and ready to go. Also, like all keyboard operations, keeping your hands in home position and not wasting time reaching repeatedly for that little rodent is going to be faster and more efficient than any other way.
I'm sure the same capability as OFR but with thumbnails for use with image files is out there if you're determined to find exactly what you wanted, and there's a boatload of them that are all free...