As far as I know, the airlines in my country not "decorate" their planes in a special way, they only put their logos and trade name, so as people could identificate them.
Last year, I saw and even I coud take a photograph, of a very odd plane. It was from a russian airline, S7, and we could consider it really decorated. It was all painted in a bright pistachio green colour. The silouette of some passengers carrying their luggage was drawn on one side, in a dark green. The trade name, S7, was in red coluor. This plane is known between the people keen on plain decoration as "THE LITTLE SHOES PLANE". I don't know why!