There are now large fences on the platforms to stop passengers straying to close to the fast lines so platforms 1 or 2 are your best bet for photography.

There is a half hourly service on the AC lines from Euston taking you past Wembley Yard and Willesden depot. You can then go back on the DC lines taking you past the Wembley depot, Royal Mail terminal and the other side of Willesden depot.

There is a toilet on platform 6 and there are barriers to get onto the station. Parking is restricted. There are a number of shops nearby to get something to eat and Harrow on the Hill station is a short bus ride away from the stop outside the station if you want to go into Marylebone.

London Overground have now taken over the running of the station. Barriers are on both sides of the station.
A loo is in the booking office by plat 6, food can be had from a kiosk on the footbridge or from a little shop on plat 5. Fast food is on offer outside the station including the big M

Any platform of 6 is good to view Silverlink metro local, Watford/Euston Silverlink county Euston/Birmingham some stop here.
Virgin trains, south central Watford/Gatwick freight trains
also there is a footbridge to all platforms to view from.
Plenty of shops close by.