If you face the wall of little blue lockers then you're showing them your ass, which is what a gay man (or one of those “straight” guys who simply likes to “play” with boys) is ultimately looking to attain and conquer. Admittedly, this is probably the most popular tactic, but it doesn't make much sense when you're giving them a clear view of exactly what they want. Plus they'll think you have something to hide in the size department.
You can also just leave the towel wrapped around your waist and complete the change that way – but it reeks of insecurity and unmanliness- causing many of the same problems that come with undressing completely before getting dressed.
Now if you want to invert the first scenario and go ahead and face them – turning your back to the innocent lockers- then you're the instigator, you're the one people will be trying to avoid the next time you're in the locker room and they need to change clothes. Blatantly throwing the sight of your penis into full view doesn't (shouldn't) make anyone comfortable (unless you really have a size issue). That reason alone is enough to avoid it, but there are more. They may start to look at you and judge your size, which won't matter if it's judged favorably or not, you'll come out – again – losing.
If they see you with somewhat of an erection (or even a large limpness), then they may think you are sending a sign or that you get excited by being in a stuffy locker room getting naked with middle-aged men – something you don't want. If, however, you are somewhat small (or are in a small state at the time), word could quickly spread of what a small penis you have. The whole gamete of states of excitement or shrinkage could fall into these two damaging categories and –once again- you come out losing in the end.
All this applies to those of us that don't like to nor want to engage in potentially flirtatious behavior with middle-aged men in stuffed locker rooms as we change as quickly as we can (to avoid this whole futile, strategic game) in and out of our clothes. If, however, you are into this sort of thing (the gay thing), disregard this notice entirely and freely pounce and frolic around the locker room completely naked and hum your favorite show tune – just make sure I'm done changing and out of the room.
Thank you
Management