I modified some tile pieces to be smaller, and after finally figuring out how to get them to use their original textures, I get it loaded in game and realize that I can put my arms into the walls somewhat and my head breaches the ceiling when I jump. Is there any way to modify or make a new collision mesh?

I'm really getting tired of all these work-arounds and expected more when waiting for the CK, at least an exporter for max...

Expecting more then just the editor was a fool dream. weve had to deal with workarounds since morrowind. They cant release everything they work with for legal reasons, so that means workarounds must be done to achieve the same things.

Wow with all those posts I might've hoped you'd respond to my question rather than my statement. I've been looking online and even on these forums people just mention "work-arounds" for collision meshes but nothing on what those work-arounds are. Anyone?

Right now (most) architectural collision isn't editable. There's a new type of havok shape used in Skyrim, and the tools need to be changed to be able to work with it, no timeframe on when that will be, sorry.

You have several ways to work with collision for models you are bringing into the game

1. Use an existing model Collision Mesh (bhkCollisionObject) that is close enough to your model size and shape (good luck with that)
2. Create your Collision Mesh in 3DS using the Convex Shape option. Sometimes this is acceptable. You will have to reduce your mesh down to somewhere around 10% of the original mesh, and fine-tune by process of trial and error. This is not an exact procedure, but results can be satisfactory.
3. Forget about creating/modifying Collision Meshes and simply create Collision Primitives in the Creation Kit. This is the best method for architectural models and similar imo.