I have a T42 and, while this machine is getting quite old, it still runs great with Debian. I was just wondering what neat modifications people have done to T4x series Thinkpads that don't necessarily involve performance. For example, how hard would it be to replace the LEDs on the bezel/lid, or wear every key down so they are uniformly blank? If anyone could offer any advice or suggestions on how to improve the look of this laptop I'd appreciate it.

Before one can discuss aesthetic mods, one has to understand what's aesthetically displeasing in the current look.

Depends on the model. I don't know about the T4x, but for the X4x and X6x they're small LEDs that are surface mounted to a board within the lid assembly. With the right gear I imagine it'd be pretty easy to remove them and attach new ones to the traces -- but first you'd have to figure out the electrical requirements...

As far as the keys, well... that depends on how fine a grit of sandpaper and how much free time you have.