Provided your image files aren't too big, shouldn't be a major problem. Format a 1.44Mb diskette in the PC, then insert it into the Mac, which will recognise it as a PC diskette. Then simply drag and drop the files you want to transfer onto the diskette icon.
The Mac will write a number of files and folders onto the diskette, so when you get it back to the PC, use Windows Explorer to open up the image file. Works for GIF and JPEG files - you sometimes need to specify that they should be saved as PC JPEG files from the Mac Application that created them.
Sorry not to be more specific - everytime I need to do this I kind of fumble my way through it and can never remember the next time exactly how I did the previous time.
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Feline
(I Sit, I Watch, I Smile)