Just downloaded this, Just a note, The map folder was empty, and did not contain the Thwomp map as stated here.
Otherwise Good job! All the Icons are great, and Ill get to checking out the models ASAP.
I've downloaded this pack once today and got the same issue as you. Guess what I did then, I downloaded it again, and I got the Thwomp map included.
So you probably had some unknown issues with your connection while you downloaded the pack.
Re-download it again and your issue will be solved.
Oh, and if you're using that crappy zip reading explorer-like thing that's built-in in Windows XP and later, do yourself a favor and stop using it. Download a proper ZIP reading software instead, like Winzip, Winrar, 7Zip or UltimateZip. The latter two are free.