I just love how you can almost customize anything in Star Trek Online. Just recently, I felt kinda bored with my character's uniform so I decided to give him a new one. Fortunately, the initial uniform change is free and you'll just have to find a Tailor NPC to do it.
A nice thing about changing your character's uniform is you can also change the uniforms of your character's bridge officers. This will allow you to match your character's uniform with your bridge officers. Having the same uniforms or matching uniforms will make them look more like a Team in away missions.

As you can see from the screenshot above, my character and his bridge officers are wearing the same uniforms. The minor differences in colors is to show the careers of each bridge officer. Red is for Tactical, Blue is for Science and Yellow is for Engineering.
Most of the uniform pieces that I used are from the Enterprise series. Star Trek: Enterprise is the series that followed Star Trek: Voyager and it aired for four seasons.
The screenshot below shows my character with his away missions team. Star Trek Online has both space and ground missions. I kinda like the space missions better because of the amazing space combat but ground or away missions are nice too.

Just remember, changing uniforms for the first time is FREE and the same goes with your character's bridge officers. Succeeding uniform changes will cost you a lot of energy credits so make sure you are happy with your initial uniform change.