Something that worked in Opensim 0.8.x : if you select "Include textures" during a mesh upload, you get a copy of the uploaded textures in your inventory, under the name " Textures".
In Opensim 0.9.x, it's not the same. If you select the checkbox, textures are uploaded and assigned to the mesh in world, but you don't have the textures in your inventory, so you can refer to them anymore.
The solution is to add an undocumented setting in OpenSim.ini :
MeshModelAllowTextureToInventory = true
The setting will be documented in next release, in reply to the opened issue: http://opensimulator.org/mantis/view.php?id=8535