If you are choosing a new light fixture, or bedding, or art, how important is it that everything match? I would suggest that as long as the various pieces coordinate with each other they do not have to be the same and in many cases it is better if they are not.
If your comfort level with decorating is low, sticking to a packaged set or buying the complete furniture placement as shown in a store may be just the thing for you. On the other hand, why not try your hand at putting things togetehr for yourself? Get a decorator’s advice to set you on the right path, and go for it.
Conflict or utter disdain between the elements can ruin your room, but healthy variance will add to the room’s dimension. It may depend on how you want your room to speak to you; sameness can be more peaceful while variety can be more interesting.
Let’s say you are picking out overhead lights. Lights are often available in a series so that there may be a flush mount, semi-flush mount, sconce and two to three sized chandeliers offered. While it may be appropriate and certainly will be easier to make all your selections from the one series, choosing an alternate piece which coordinates with yet stands out from the others can add an element of interest and specialness for one or more of the fixtures. As long as they relate by having the same metal, shade or shape, they will speak to each other and therefore be a great fit.
Many times we have most of the room in place and want to add in one or two new elements such as a new chair, cushions, rug or art. Same advice applies; choose the new pieces to speak to the existing pieces. You’ve heard many times to use the same colors and finishes to tie things together. You can also use the patterns and shapes in the room to do the same. If you have fabric in the room which has graphic lines for example, compliment with accessories which mirror the pattern. Maybe it is the theme in the room which ties it together, such as artwork which portrays nature married with natural accessories such as driftwood and jute.
Style and size are also important. Rather than buying a matching couch and love seat, I prefer to choose a couch and coordinating chairs if space allows. Seat height, arm height and shape, back height and legs of the pieces will determine if these pieces are going to feel well suited to each other. Side tables are considered based on height to complement the soft pieces.
Even eclectic spaces need some level of unity. Mixing old with new and funky with serene will work best when there is a common thread. It may be that many of the pieces are made of the same material, the proportions of the furniture are consistent, or through the flow and functionality of the room.
Does everything need to match? I say no. Be adventurous, enjoy your decorating, and love your space.