I've seen an addon that replaced the standard world of warcraft stonish backround of the loot table, character gear log, and friends list tabs etc. with a lightly purpleish, sort of solid shiny backround. anyone have any clue what i'm talking about?

bump

I know Skinner can change the skins of look of things like the spellbook, don't know about a purplish tint though

Anyone know a addon that makes things bigger such as bagpack ?

Skinner can do this.  Likely you saw somebody's UI that was running skinner and the person adjusted the background texture or gradient.