As has been mentioned, you will need to specify your goals. I can tell you what you will look like if you just train to be lean and strong for the next five years...you will look like me. I'm skinny, but I don't care at all. I'm 5'10 and right at 175, never over 7-8% bodyfat at my fattest (when I weigh around 182-185).
There are pics of me floating around here somewhere...maybe someone will post them and you can see if its the look you want.
Most people want to be a bit bigger than I am. Personally, I feel great at 175lbs. I'm fast, whippet lean, strong for my weight, without headaches, etc. I use primarily fina and oxandrolone, with a tiny test base (200mg/week). I got really ripped the first few times with high doses of winny, but that is very unhealthy and the same results can be achieved with fina, which is a much safer drug than winstrol.
One thing I can say about staying lean while you train--you will have a dense look to your muscles that a lot of bigger lifters do not have. I am not big, but my forearms look like steel cables and I generally have a christmas tree in my back when standing relaxed if I am on cycle. In the sauna, people guess my weight at around 195. That's twenty pounds heavier than I actually am.
Detail is the envy, bro. Stick with lean musculature...let the size come at its own pace. My suggestion is to focus on squats and deads for about a year, along with sprints to keep your heart in shape and keep you really hard looking.
165 is thin at 6', but not too thin. Don't be fooled by mass monster wannabees or pro bodybuilder standards unless that is really what you want for yourself. Should you gain weight? I think about twenty pounds of super dense muscle and you will be about right, at least in my way of thinking. Take your time...three years...put it on dense and strong and slow and deliberate. It will stay when you are off cycle that way.
In fact, the only thing that changes when I am on is that I look harder and get about five pounds heavier. I only cycle to prepare for photo shoots, films, and to maintain a generally hard, striated look...I do not cycle to gain any more muscle. I gain roughly 2 lbs/year. People laugh at me when they read that, and when they read my stats, but I'll put my pic up against anyone on or off cycle. I'm thin, but I am in shape.
In the end, its all about what you want for yourself, not what other people think you should want. My suspicion is that you are proud of your body right now. You should be. There are more members here who wish they were lean and ripped, even if it meant being thin, than will ever openly admit it. You look good right now in the context of general male physiques, and it is only in the context of purposeful aesthetic development that one could say that you are lacking development. In any case, the main issue here is maturity. It was said earlier in this post, with your genetics, you can take it either way. Your muscle bellies are full and long and your bones and joints are small and prominent...you're head is not oversized and you have height, so for you the sky is the limit.
Just what ever you do be sure you do it the right way, with emphasis on training technique and diet. Stay lean if you can, you will NOT regret it. Take it from someone who is lean and ripped at 35 and still getting somewhere with small doses and infrequent cycles.