Ya know, even though his eyes are closed, that is 
still a fantastic cel.  
He doesn't wear the shirt cause he's so darn 
*hot* ;)
Actually, I believe when he first meets Miaka and 
the others, it is winter, or at least late fall, 
and cold out.  I think later on it is summertime, 
or at least spring- Miaka goes without her jacket 
then, and Tamahome goes short sleeved or even 
sleeveless in a couple episodes.
I actually like the white shirt. Hence the OAV 
cel ;)
Here's my long haired TV tama.  :O