SL can sport some pretty impressive graphics, polygon-wise. The avatars are detailed and high-poly. Objects can be as detailed as the creator likes. Really, one of the big things SL is lacking in comparison to many videogames is effects.
Now, it's up to Linden Labs to implement hardware driven lightbloom, motion blur, shadows, camera effects, and more complex video filters to pull off effects like night vision, or heat vision, or what have you. However, content creators within SL can create simple, but still interesting visual filters in the form of HUD attachments.
Coadey Concord made an excellent "distortion" filter wich gives the user a widescreen view of SL, in addition to an eerie film grain effect straight out of the Silent Hill games (literally).
This is awesome, fantastic, so what am I asking for here? Well, the problem with any such filter is that while you're wearing it, you cannot interact very well with anything inworld. You cannot click on prims or other avatars. You cannot open doors, you cannot use vendors, you cannot build, you cannot right click on people to see their profiles, you can't even click on your own avatar.
I'd like to see a HUD attachment point, or an option somewhere, which lets you were such attachments, without them interfering with inworld interaction. I'd like to wear my film grain, sepiatone, hazeyvision filters all without needing to constantly be taking them off to do the most common SecondLife tasks.
It seems like it would be simple for Linden Labs to pull off (I could be wrong here!), so it would be nice to have that option while we wait for more advanced visual effects which will make SL even more visually appealing and immersive.
http://steampowered.net/penny/distort.jpg