OK,I guess I'll be the one to write a small book here
Ok,everyone gave great examples of what exercises to use. But honestly,you may think I'm crazy but you know what made my arms go from thin long lanky looking 17.5" arms to around 20 inches. 2 things.....a massive weight gain and I took a few months off from working out arms specificaly. I did all big power movements with big weight. The only thing I would do specificaly for bi's would be hammer curls with the rope attachment on cables. I do a movement that you'll sit like your doing a row but where my back would be at full contraction, thats where I begin the curl. When the rope handles touch my front delts thats where I squeeze. To me it feels like it forces your biceps to move the weight by leaning forward. This was the only bicep exercise I did for those couple of months.
One thing I'm sure everyone has told you already,or I hope atleast,is that your not going to gain mass on your arms unless you gain weight. You can change the shape of certain muscles without gaining weight. But if you want to gain size your going to have to gain some decent weight. Theres a rule of thumb as far as how much weight you need to gain to grow your arms "X" amount. For example 1 inch will require 25-30lbs of weight gain. Thats not exact,it's just an example but you get the idea. I went from 17.5" arms to 20" by going from 185lbs to 248lbs. And I have naturally muscular arms,but not very large arms. I gain on my arms really quickly but when I start getting up to whats considered "big" for me it gets harder and harder to gain. Arms are funny. I've made my biggest gains when I wasn't even trying to make big arm gains. I think it's because it's so easy to overtrain arms.
Also maybe try training bi's and tri's together. I just trained bi's and tri's together a few weeks ago. Man if nothing else it gives your arms a "back to front" pump that had my arms feeling like they were gonna' explode! Hey,it's something different,right? Good luck,man!