Given a folder of images, pico will generate thumbnails of size 64x?? (keeping the aspect ratio) and place a index.html file in the folder of images (along with jquery and angularjs files). You can then fire up a browser, point it at the folder, and navigate the images in that folder.
Get a JDK and Maven, then perform
mvn clean install
This will place a file called pico.jar into the target/ folder.
java -jar pico.jar <name-of-directory>
Pico will recursively generate thumbnails and index.html files. Pico will not overwrite existing thumbnails. The thumbnails are stored in a folder called _thumbs.
To view your images, you have to fire up a webserver that serves the contents of that directory. On systems with python you can do:
python -m SimpleHTTPServer
in the directory that contains the index.html file. Pointing your browser at the local file will not work.
Pico is in the public domain, do with it what you want.