Version:           2.4.2 (using 4.4.2 (KDE 4.4.2), Kubuntu packages)
OS:                Linux (x86_64) release 2.6.32-19-generic

Most image viewers that I'm familiar with use either PageUp/PageDown and/or CursorUp/CursorDown to advance to the next or previous image when viewing images, in particular in fullscreen mode.

One can easily configure Gwenview to do the same.  Alas, this breaks browse mode, since I no longer can use the page or cursor keys to navigate the cursor in the browse window.  (Note that if the current folder contains a mixture of images and folders, the behavior of PageUp/Down is entirely unpredictable, as sometimes PageUp will behave as "move cursor multiple rows" and sometimes as "move cursor to next image".)

I strongly suggest to ignore certain key bindings in browse mode, including at least cursor keys, PageUp, PageDown, Pos1, End, and Return.  Alternatively, you might want to consider to use entirely separate keyboard shortcurts for each of the three Gwenview modes.

(I've found other bug reports and wishlists, e.g. #223291, that seem to share my general sentiment.)