To make your images show up on other services / devices - including Twonky run the excellent 'Save Album Art as folder.jpg' script by Doug Adams, available for free here: http://dougscripts.com/itunes/scripts/d ... bumartjpeg
I've converted my entire music library - over 8000 tracks - now they all show up in Twonky and iTunes continues to function as normal

I hope this helps
DJ