Yeah, forgot the default behavior on blocks is stupid. Fixed that.
https://dl.dropboxusercontent.com/u/57416963/TabulaRasa-1.6.4-1.0.0.jar
Didn't bother renaming, sorry.
Anyways, as far as textures go, your string should read <mod>:TextureName (no .png)
and for blocks, that'll end up in mod/textures/blocks/TextureName
for items, it will be mod/texture/items/TextureName.
So basically that "/" should be a colon, and then in the /textures/blocks/ subdirectory of tabularasa in your assets folder, or at least I assume. Check another texture pack for the directory structure, but I believe I am correct.