AS it is I have not done anything external to the van...
The only real 'mods' (if you can call them that is swapping all interior lights of LEDs and the park lights with super bright LED items as well, seriously these piss you off when I'm behind you at the lights.
All the wood panelling has now been covered in marine carpet to give it a less tradesman feel and more of a sedan.
It's strength lies in its almost complete stereo, right now a 1500WRMS system running a 2 x 100wrms amp powering a pair of 80WRMS @ 4ohm 6.5" AudioLine splits in the cab, these alone are enough to fill the cab with more noise than you ears can handle... not being content though I have a 2 x 150WRMS amp powering 4 Sony 440Wpeak 6x9" @ 2 ohms, it's close to the limit of what the amp can drive but ok. Finally to give some oomff to the lot is a 1000WRMS D-Class driving 4 12" Kicker subs @ 2ohms. Over all I'm reasonably content, but there is still some expansion to be had.
I still have another 2 x 100WRMS and another 2 X 150WRMS amp lying around the place doing nothing so I'll throw them in, as such I will effectively double my speaker system another set of splits in the cab and 4 more 6 x 9's, My D-Class has enough grunt to allow me to add two more 12" subs... Final system should be 2000WRMS, with 2 pairs of 6.5" Splits, 8 6x9's and 6 12" Subs... should pump out a bit of volume. All in good time.