Paul Krohn on the WELL has discovered an interesting way of recovering 10MB of RAM on his OSX machine: use a TIFF for a background in the Finder. According to his research, JPEG background textures can occupy up to 10MB of RAM.

Memory usage note: setting a JPEG to be your desktop background can consume 10 MB of memory, even if the JPEG itself is smallish (in my case, 44 KB). I guess it consumes (screen resolution) x bitdepth bytes.

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Yeah, my testing was empirical: how much less private memory does the Finder consume with a solid blue background than it does with a picture of Thomas enjoying his lunch?

http://www.daemonize.com/familypics/index.php?bigimage=29

It stands to reason that the entire uncompressed image has to be held in memory, otherwise I guess the jpeg would have to be decompressed every time part of the desktop was revealed, so that part could hae the appropriate part of the image painted in.