Which would be ideal for a warlock whose patron was from Stygia (Stygia's the ice level of hell, right? With the guy frozen in the iceberg?).
Well, given that she had only one cold power (a daily), I wouldn't say it was that ideal for this theme either (not sufficient, at any rate). If that was the theme, a better move would have been to ask a houserule to have Hellish Rebuke become 'Frostbite' (same power but cold damage) rather then dispensing with the pact power altohether for two bland at-will, IMO. I don't remember that her demon was cold themed, though. I remember no theme, in fact.
The most memorable and distinctive thing about Tsi'Ri was her familiar which was a third eye with independant will. It differenciated her from all other warlocks and I
really liked it. So I tried to reinforce her most distinctive feature by granting her a tattoo with appropriate powers and fluffed it as an extension of her mystical third eyed. I was really happy about that treasure choice... but the player
sold the tattoo! It left me rather nonplussed, I tell you that!

Elecgraystone prefered having 20% of its value in cash and stick strictly to the wish list.
There is no denying that PC was very effective, though. And there is nothing wrong with his/her choice. This anecdote just illustrate a difference in philosophy. That mini-clash between her style and mine lead to some of the frustration expressed by the player in the recently ressurected thread about letting players trade items. Hopefully, that's not why the player left L4W (Tsi'Ri did go on another adventure under a different DM before going MIA). Not sure I would do anything different, though; I am entitled to my own philosophy and freedom.
But this why I am
opposed to removing the houserule. Personnally, I'd never make a warlock that dispenses with the pact's signature power altogether, but that's my choice. People should always have as much freedom as is reasonable in a communal gaming world. Anything that pertains solely to the PC should be left entirely in the hand of the player. It's kind of the Habeas Corpus of RPGs!