Whenever I'm tasked with decorating a room, I break it into pieces and think of the pieces as relatives (sometimes they are sisters or brothers, sometimes cousins and even mothers and daughters and fathers and sons). To explain this in a more technical way, I mean I think of them as being separate pieces, with different personalities, which have the same DNA.
Maybe that is still confusing.
Let's just say every piece of every room in my house fits together but there's little rhyme or reason save for a lot of color matching and hue coordination.
Take for example, this 1/3 of a wall in my bedroom, this is one of my favorite vignettes. This piece of art was painted by my great grandmother and I'm lucky enough to be the current safe-keeper of it. The hats are a small piece of my wide collection which I rarely wear but love to stare at (I do wear them, but not as much as I should). The straw number doesn't even fit my head and belonged to my husband's grandmother and the other two I purchased for a combined total of $10 from an antique store in my home town.
Pick a color scheme, separate the room into pieces and move forward piece by piece. The decoration process might take a little longer to finish (or it may never be finished) but it is much easier to manage one relative at a time than to attempt to tackle a whole family.