xzgv is a picture viewer for X, with a thumbnail-based file selector.
It uses GTK+ and Imlib. Most file formats are supported, and the thumbnails
are compatible with xv, zgv, and the Gimp.
xzgv differs from other picture viewers for X in that it uses one window
for both the file selector and viewer. It allows both scrolling
and fit-to-window methods of viewing large pictures, and it
doesn't ever mangle the picture's aspect ratio without you telling it to.
It also provides extensive keyboard support.
For using the keyboard, this is almost certainly the best viewer.
It also doesn't skimp on the mouse stuff, either.
You can click on a picture to view it, or drag the picture around
to scroll (or use the scrollbars).