Way to lock a folder’s icon without making its contents Read Only

As mankoff said, the large size is probably a resource fork (with things like previews). To confirm this, use the Terminal command ls -l@ /Volumes/Database/WebFolder/imgs/confirm.gif -- you'll probably see something like this:

$ ls -l@ /Volumes/Database/WebFolder/imgs/confirm.gif
-rw-r--r--@ 1 www  www  539 Nov 18 09:39 /Volumes/Database/WebFolder/imgs/confirm.gif
        com.apple.FinderInfo     32 
        com.apple.ResourceFork  40748 

If it doesn't show a 40kb resource fork, report back so we'll all have a better idea what's going on.

As long as the image is just for web use, a big resource fork isn't really an issue, since the web server will only serve the data fork (which is just 539 bytes long). If want to compact the file anyway, use the command xattr -d com.apple.ResourceFork /Volumes/Database/WebFolder/imgs/confirm.gif to remove the fork.

I think I've found a workaround!

First off, install osxutils bundle which is a bit dated (2005) but nevertheless it works. (see the osxutils contents and man pages)

Prepare the PNG to ICNS^†—ironically you can use sips^‡. Then use seticon from the osxutils bundle to change the icon:

$ sips -s format icns FIN.png --out FIN.icns
$ seticon -d FIN.icns FIN.png

The seticon also changes the file's attributes, ie. using SetFile -a C isn't necessary.

†: Using a PNG as a source file for seticon changes the icon to a generic PNG icon, even with -d option. Furthermore, using seticon FIN.icns FIN.png changes the icon to a generic ICNS icon. (Consult the seticon's man pages)

‡: NB: the source file must be a square and possible side-lengths are: 16, 32, 48, 128, 256 and 512.