I use GQview
for photo management of several 1,000 photos, as it enables me to associate keywords easily to photos and is straightforward to use (very quick to browse through directories of photos) and super stable. The GUI is rather old-fashioned looking, but looks are secondary to functionality as far as I am concerned. Actually, there is also a fork of GQview called Geeqie Image Viewer
with additional features. I haven't tried it, but it looks very good. Both packages are in the Entropy repository.