I am releasing my source code for a full fledged Flex 3 image gallery along with a PHP based Minimal Image file manager page with upload, delete and automatic thumbnail generation features. I had made this while learning Flex, but it is very usable in many projects.
To see it in action, download, extract and put the bin-debug folder under your web server. There is a folder called "Admin" inside "bin-debug" folder which has the PHP part responsible image upload, XML file generation and auto thumbnail code. To manage the images, use filelist.php in admin folder. Tested with JPG and PNG images.
Download Source code - 8.78 MB (along with sample images)
Please drop me a line if you are using this anywhere.