Hi, and welcome! If yoiu go to UBRS (
http://u-boot.realsimulation.com )
and look around, you will find many good downloads there (Skins, mods,vid's..).
To apply the skins: When i want a new skin, i just downloads it, then i copy the contents of the download (usually a file called Data) into the SHIII root directory(overwriting the Data folder in SHIII: take it easy, it only affect the subs skin, and nothing else...!). Then it will copy itself on to the respective sub.
I hope this helped....
Icebergs: Well, i think everybody here on subsim are on the lookout for icebergs in shIII, especialy in the campaign mode. In the single missions there is IIRC one mission with icebergs. (Mates, please correct me if im wrong..).