According to this Ubuntu howto[1] it is possible to create nautilus thumbnails for OpenOffice documents just as is currently done for PDFs and images. It would be great to see this distributed as part of the Gentoo OpenOffice ebuild with a gnome USE flag. 1. http://www.ubuntuforums.org/showthread.php?t=76566
This is really something which should be done properly upstream, please request this in the OOo Issuezilla
I have now learned that this functionality is provided by libgsf. Version 1.14.0 (currently latest in tree) provides thumbnails for MS-type documents, version 1.14.1 adds the OpenDocument documents.