Pictures as promised

Here are the pics of my birthday cake.  It tasted yummy even if it didn't look it so much.  I need input from you baking pros so I can do better next time around.  I baked lemon cake (Duncan Hines lemon supreme to be exact) and then lined the cake pan with plastic wrap and "spread" softened vanilla bean ice cream in the pan.  I covered it with another layer of plastic wrap and returned it to the freezer for several hours.  I leveled one layer of my cake then layered the ice cream between the layers of cake and attempted to frost the cake with buttercream frosting.  You can see that it didn't spread on all that smoothly on the sides and then the ice cream began to melt and that really messed up the frosting effort.  I stuck the whole thing back in the freezer for a spell while I contemplated how to make the cake look presentable.  I tried slathering a bit more buttercream on the sides but it just wasn't meant to go on smoothly.  I quick piped a border, added sprinkles (what's ice cream and cake without sprinkles?!) and piped Happy Birthday with the bright blue frosting leftover from my cousin's cake last week.  Ta-da!  Surely, there must be a frosting specifically for ice cream cakes--maybe something a little lighter than buttercream like a whipped cream frosting?  The cold buttercream was a bit too rich, in my opinion.  If anyone has any suggestions or tips I'd love for you to share them!
You might have noticed the six candles.  For all of you mathematicians out there:  4 represented the tens place and 2 the ones place!