Not that it's your fault they didn't include the arrow, but when you rent a car, you want to walk completely around it anyway before driving away. Otherwise they may try to stick you with pre-existing damage that wasn't noticed the last time the car was turned in.
(I've heard it's a good idea to shoot a video of the walkaround with your phone, but that seems OTT.)
I have never rented a car where the rental person didn't do this with me. Nobody is going to remember what side the gas tank is on though a week later when you fill it up.
I've never rented a car where the rental person was even near the car when I walked it. And I rent cars every few days...maybe the lack of personal attention is an airport thing.
I thought you were supposed to take the pictures after you scratch the car, so that you can "prove" that the damage was there before you picked it up.
My point being, what are photos or videos supposed to prove. If the car is damaged before you pick it up, and there's some reason that you are still taking it, then you should get the agency to sign something attesting to it.
Oh, that's only if there's a borderline case. I.e. if there's something you didn't really see when checking yourself (nor remember), but can find in the pictures later, if necessary.
Even without an arrow, the tank is always on the same side where the filling pistol is on the picture next to the fuel gauge. It's on the right in yours.
No, I don't think that is true in general. I think the nozzle is almost always on the right side. Unless there is an arrow, the designer probably neglected to explicitly indicate anything.
I use a service called Car2Go quite often which rents Smart cars exclusively. For some reason they decided not to include the little arrow.
http://0.tqn.com/d/cars/1/0/6/9/1/ag_08fortwo_speedo.jpg