Gmail is one of the best solution to handle so much flood of mail, but an inconvenience annoys me these days.
The size of the preview thumbnails of the image attachments.

Because I receive many of mail with atattchments including the automatically converted FAX as jpg, I wrote easy greasemonkey script named gmailEnlargePreview to make the thumbnails larger.

Please try if you like this. The script can be get from :
http://userscripts.org/scripts/show/30437

You can also get Japanese entry from :
http://blog.hippo.fm/2008/07/gmail-greasemonkey.html