Very nice! I'm impressed you've been able to do all that in a short time. Shadows are generated by the game based off of a ship's tangent map, and to a lesser extent it's DA (lighting) skin. Admittedly I have no clue how to make engine particles, except that you can make them in the good old Particle Forge;
this thread might be helpful.
Mainview icons can be found in Unit_Infocard2.tga though you can easily make your own file and use that. You can get really detailed icons, like Sins' default icons and the Marauder/Lambda icons (made by GoaFan), using a nifty combo of the regular RGB and alpha channels. Or, if you want something that simply works while still looking good, you can make the icon in the RGB channel and then copy paste it onto the alpha channel. After you make the icon, slap an entry into the MainViewIcon-Ship.brushes file and you are good to go. If you are wondering what the difference is between the infocard icon and mainview icon in SoGE, if I'm right that was done to make things look neater on the empire tree/infocards; using mainview icons works just fine for those however.
As for Titans, they're coded just like any other Titan, the difference is in their spawning method, which is via an ability on the shipyard. Basically, the short story is that they have a complex buff chain, including a passive ability on the Titan(s) itself, to ensure that only X of said Titan can be on the field at a given moment. The best way to get this done, without putting in a spawner without a cap (which is much simpler), is to copy/paste an existing Titan's ability/buff chain and rename it to your own Titan, while modifying times and costs accordingly. If you have an IM client, Steam, or can use IRC, I'd be more than happy, and would prefer, to walk you through this in real time; it would be much easier than attempting to explain this over a forum.
If you want to help at all with SoGE, I'd love to have you on board for whatever you'd be willing/want to do. Plus, if you ever feel like releasing that Legacy faction, I can help you get that up and posted someplace; there are many out there who have been begging for such a mod in fact.
