With newer icon themes most icons from the preferences dialog are missing as thunar-volman 0.3.80 does not conform with the icon naming spec from http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html Attached patch fixes the problems. tvm-dev-tablet.png can be removed.
Created attachment 3178 icon-naming patch for thunar-volman 0.3.80
Problem also applies to latest git.
Unfortunately, I don't have the time to seriously maintain 0.3.x, but at least this is fixed in master now and will be ready for the Xfce 4.8pre1 release. commit fc6906c4c9ae1da2d5793cc9427bd19aa023cc0a Author: Jannis Pohlmann <jannis@xfce.org> Date: Sun Nov 7 14:40:31 2010 +0100 Fix incompatibility with the icon naming specification (bug #6786).