I don't think you're missing it. I don't think that the terms "open" or "concealed" are defined for 30.06 or 30.07, unless I'm missing it too. However, under the unlawful carry by license holder section,
http://www.statutes.legis.state.tx.us/Docs/PE/htm/PE.46.htm#46.035, they don't use the term concealed but instead say and have said it's a violation to "intentionally display the handgun in plain view of another person in a public place." I think that most have considered that to be the guide on what is concealed or not. I am not a lawyer but, pretty much an opaque material covering the surface of the handgun, so that no part of the handgun itself is intentionally visible, I would think, should be considered concealing.
I would not worry about general, normal printing at all.
Even very obvious printing was a common thing, at least among activists, before open carry passed, and at that time had to be considered concealed carry to be legal. I don't recall any instances of activists being hassled over printing or using form-fitting coverings.