For my daughters 4yr party we did a crayola theme. I bought different color paper and cut crayon shapes for the invitations. For the cake I made a sheet cake and put a box of crayons on top. I cut out larger crayons and placed them around the room with all the colors of the crayons written on the crayon. Bought balloons the color of the crayons.  I put white paper on the tables and let the kids color anything they wanted on them as a keep sake for my daughter. For the party favors I bought little buckets in the colors of the crayons.  I spelled out crayola on the front of them and each child got a box of crayons and a coloring book.  The kids had a blast and it was something to do inside, because the weather is not great.