I went pretty simple on Lincoln's birthday cake this year. I was inspired by this cake but wanted to have darker buildings, so I decided to pipe chocolate into rectangular shapes to form the skyline around the perimeter. I've found a few tutorials on piping chocolate, but basically I just bought a bag of wilton candy melts (they were way cheaper at Michael's), put them into a plastic sandwich bag, and microwaved until they got soft. I didn't want the chocolate runny and scalding, so I watched it closely and kind of kneaded the bag to get the heat spread and chocolate melted. Then I placed a layer of parchment paper over my template (I just drew some rectangles in word). To pipe the chocolate, I cut a small piece off a bottom corner of the bag, and then piped the chocolate into "rectangles." It turns out I'm not all that great at piping, but oh well.
To make the "lights" on the skyline, I went the easy route and bought a tube of Wilton Ready-to-Use Icing. I used my regular tip and coupler, and piped little dots all around the cake. Then I went back and kind of tapped them down so they weren't as pointy.
That's about it. I put some superheroes on it and a little "4" candle and called it good. Lincoln LOVED it, and that was my priority.
Another successful birthday cake venture!