I have been making my kids' cakes for years now. Here are some of them. It's always fun to make something they have requested or having to put something together because nothing exists out there yet for the newest character(s).
Tinkerbell and friends tree house. I used a giant cupcake mold to make this. The doors are actually the windows to a castle cake mold set we have. To make Tinkerbell's friend stick we put a little icing under their footing.
My twin boys turned 8. They wanted a Mario Kart 8 party and cake. I made rainbow road figure 8 out of sour strips. I left the two outer sides icing free for the birthday boy who doesn't like icing. Dollar tree party favor racing cups. Reused toys they already had (Mario, Luigi, Peach -all happy meal toys- and the mushroom). I've had the star candles from a clearance sale for a long time waiting for the perfect cake. They loved it.
Also for my boys birthday Mario style, they wanted cupcakes so they could have "big man" mushrooms too. I do have one birthday boy though that has decided he no longer likes/wants icing so we had to have some naked but I still put the dots on a few.
My daughter turned 11 and wanted a Frozen themed cake and party. She told me how she wanted it to look and we worked around that as best as possible. The inside of the cake is purple and teal swirled. I forgot to take that picture.
I have twin boys and for their 7th birthday they wanted a race car cake. One boy wanted red the other wanted blue so we split it down the middle. I used black licorice for the wheels and for the racing stripe separating the two colors. I have one boy who doesn't really care for icing so I left the bumper corner area clean of icing for him. I used a racecar cake mold. We put 7 candles on the front hood and 7 on the back trunk so each boy had his own candles to blow out.
My daughter wanted a "Monster High" type of cake. She told me her design, what colors, what size, what shapes and everything. She turned 10 and was very specific of what she wanted. So of course Mommy delivered. I think it's cute and it came out tasting good too. The two corners were left uniced for the little brother who doesn't like icing.