The best place is on the balcony of the Rhoose Flying Club as been previosuly said from outside the airport.
Inside the terminal the best place would be in the landside bar on the first floor which you can see right over to the British Airways Maintenance Hangar.
Airside bar shows good views of stands 1-7
According to the South Wales Aviation Group website these are the current stored BA aircraft at CWL.
G-BNLB B744 (Red nose from the Red nose day charity pull)
G-BNLC B744 (Titles removed and engineless southside if i'm right)
G-BNLU B744
There are a few other aircraft inside the hangars also which maybe positioning in/out on the day you visit if your lucky.
For a view of the departure boards from last friday
click here