Large art will create impact and set the colour scheme for your whole room. With this in mind, it would be best to choose the large pieces of furniture and your floor rug with this the colour palate in mind ensuring the art is the stand-out. You can then balance out the room with additional pieces such as cushions and accessories to tie the whole look together.
Choose your feature piece of art for the mood you want to create in the room; blues and greys create a tranquil and calming space; greens and browns for a homely and welcoming space; a mono theme for an executive and minimalistic space; bright and bold for a upbeat family or entertaining space.
One large piece of art creates impact as does two medium pieces.
Its best to match the frames or for a more relaxed feel to the room try having complimentary frames but not identical. For drama, have a single large piece of art as the only statement on a wall with no additional furniture items to distract from its impact.
There is no right or wrong except to ensure the scale of the art is right for the room and wall size to create the mood you are after. Have some fun with the process of choosing by creating a mood board to see if the pieces you like work together and then also consider your frame types.