You can use CASCExplorer to extract the WMO file, then open it with 010 Editor.
You can download 010 Editor from
HERE.
You will also need 010 Editor Template for WMO.
You can download all 010 Editor Templates from
HERE.
You will have to open 010 Editor, open the .WMO file, go on the top menu to Templates - Open Template, open the WMO Template, then Run the Template and then open the structure of the WMO and search below for Textures / M2s used (M2s are the objects). Just play a bit with the 010 Editor and you will figure out where you can find them.