Created attachment 101777 [details]
Mockup Nautilus

Hey,

The feature to change that is in Gnome since version 2.20.
You can find it in your gconf-editor under:

apps -> nautilus -> icon_view -> thumbnail_size

it defaults to 96 and i always put it on 48 (that's the size that all other icons have as well) which seems to fit well in about all locations.

i know this because i made the first version of the patch ^_^

Good luck!
(bug report can be closed if you ask me)

Thanks Mark. Though, I think we may need an UI to configure that without GConf.

We can  add an option to set the thumbnail size in Nautilus--Edit--preference --- 'Preview' tab -- 'Other Previewable Files' field.  

One problem may confuse the user is, in this fields,  the option of "Only for files smaller than" sounds like the setting will work for files with any mime-type, but in fact it just works for images.

This is out of date - changes made in Gnome 3