Hey there, good start! Not sure if you are a drummer, but if not there are a few things that stand out to me. Firstly most drummers don’t have so many toms. However if they did, there would be more of a difference in size between them. The size of the tom directly relates to the pitch of the drum, and you don’t usually want to have drums that are so close in pitch to each other (or you could just hit the same drum 4 times instead). Also, the upper toms need to be angle down toward where the drummer is sitting. The floor toms seem to be the same size as each other. Again, if a drummer had 2 floor toms they would be different in size. I would make the back floor tom 10-15% larger as the most common size is bigger than what you have there (imho).
For the material issues you are having, does the wood drum mesh have a thickness or is it just an extruded circle? Are you using raytraced or ztransparency for the drums skins? The wood grain texture seems a little stretched and little too low detail as well. Hope this helps. Cheers.