It seems that the PDF and JPEG thumbnailers seem to generate a black border and drop-shadow around the thumbnail image, whereas the PNG and GIMP thumbnailers do not.

Can we change our thumbnailers to not include a border or a drop shadow, and just add a shadow in Nautilus instead? I think this is a better approach, as it allows us to do funky things like raise the offset of the shadow when icons are dragged to give a better sense of picking something up.

Alternatively, we should just make sure that all thumbnailers are adding the same style of border.

This is tricky, because if we want to get this right, we essentially have to match the icon theme (think about the different shadow perspectives for Tango vs. Human). Perhaps an icon theming engine would be useful, so that you can programmatically add drop shadows to a 2D image in a manner that matches the current theme.

Cheers!

Alex