People could promote whatever they wished. Those who appreciate the works of particular artists, will have ample resources to support them. Consider that there is an unbelievable amount of wasted labor under the present system which would be completely redundant under socialism. Productive labor is that which produces a tangible good of some sort that we can use in some manner. Non-productive labor is all the labor necessary to society to enable productive labor to function, such as the labor of a schoolteacher or a grocery clerk.
Unproductive labor is that which is only necessary to the capitalist system.
These and many other forms of labor would either be eliminated or amended in some manner by the future society. Under a socialist economy we will produce for use, not for a capitalist market which drives businesses to constantly raise productivity in order to undersell competitors. Products will be fashioned with care and lasting qualities, and producers will work at a leisurely pace befitting humanity rather than as peons driven by slave masters. As for the lazy, the former capitalist class will have to do useful work just like everyone else. If they refuse to contribute, they will have the choice to starve.