IIViewer is an application for X, and optionally for the Linux framebuffer device. It allows you to display pictures in a directory as thumbnails. Selected images can then be displayed at full size. It reads BMP, GIF, and JPEG (even without libraries).
FLEX-db - an enterprise Digital Asset Manager (DAM). It ingests and links metadata with files, creates thumbnails, and processes files using business rules. FLEX-db has a JSP client, Java app server for file input and output and an EJB metadata layer.