XnView is a popular free image editor for Windows that has been ported to Pocket PC and Smartphone, allowing you to edit your photos while you're on the move.
XnView Pocket is designed to help you view, manage and modify all the photos stored on your mobile phone. Considering it's a mobile application, it's surprising just how much you can do with this version of XnView. XnView Pocket lets you display images one-by-one, create elegant slideshows with transitions, organise them into different folders, share them with friends via IR, Bluetooth or email, and even capture your mobile screen as an image.
One of the great things about XnView Pocket is the sheer number of ways it lets you view your pictures. XnView Pocket has five different viewing modes - Thumbnail, List, Detail, Filmstrip and Full Screen. The buttons for navigating folders are clearly-labeled and easily accessible, and you can access all the EXIF data and use it to categorize your pictures.
XnView Pocket includes a number of basic editing tools, though these are not powerful or advanced enough to do anything too creative.
But if you're looking for a way of managing your mobile photos on the fly, they don't come much better than XnView Pocket.