not sure there is much to improve graphics if thats what you mean, but then again there may be.
you can check into the U-boat skins, there are some great skin mods out there... im currently using STEEDS, type VII black grey and white colored one. There is a winter camo i use for winter months in the game by FUBAR, ISITOL also offers a nice curvey grey on grey cammo pack i have been known to use.

good stuff there
thats about all i can offer up.
you can get SH3 commander and enhance immersion and game play.