If you want better textures, ALOT (A Lot of Textures) is absolutely essential. They cover the entire trilogy, and they make the games look fantastic by adding 4K resolutions. The Expanded Galaxy Mod for Mass Effect 3 is quite popular, but that just depends on what you are into. Also, all three games have controller mods, if you prefer to play that way. You can find everything you need for the whole series over on Nexus Mods.
Also, if you want to do some funky stuff for kicks, you can always download the Gibbed Save Editor. You can do just about whatever you want with your save through that for ME2 and ME3, at the very least. There's probably an equivalent for ME1 as well.