I also feel your pain, I love designing, I personally think its the best feature of the game.
I have been playing from the very beginning and have recently had the the first limit warning pop up and it made me quite anxious to think I might not be able to continue with my designing, I have started to try and store any decorations that were hidden behind other objects in order to bring the item count down.
I believe it's only going to get worse as more content is added, so hopefully they will be able to increase it my a decent amount.
