Here is my second try:
Linky to png file
I think this one looks slick. I made a dark silhuette around the torpedo, improving the contrast.
I have personally blanked out the alpha for the current thin black torpedo silhuette found in the "TorpedoPage.dds" file. This whole file is merely 256x256 px large, and the thin black silhuette for the torpedo, is a single one, that won't match torpedoes that look different in shape. The container for this thin black outline is also not matching the maximum width for the other torpedo alpha, so any graphics drawn for that will not cover the length of the new torpedo. This thin black outline seem useless anyway.
About colors: The black'ish warhead on the torpedoes look perhaps abit boring. Maybe some other color would be suitable. Perhaps a brass color would suit the torpedo body? I don't know what might seem plausible. On second thought, the brass would clash with the yellow stuff on the torpedo system page I think.
I have some ideas for color coding the torpedoes and I want to present a suggestion. I thought a red warhead would be sensible for the homing torpedoes, since the uboat risk (true?) being hit by it's own torpedo.
I wonder, what are the consequences of scaling up original texture files in terms of memory usage? I wouldn't mind seeing the 256x256 texture increase to 1024x1024 to perhaps get some nicer outlines.