Decorating question - house plants?

I have a handful of houseplants and would like to get more.

Some are small and some are medium sized trees (~4 ft. tall). We have a corner of the living room that is not in use so we have sort of grouped the plants there but the grouping isn't working because it doesn't really look unified.

Any ideas? Is there a piece of furniture we should use to store the smaller plants or is there a way to group the plants or change them so they look more unified?