Try to install the pallets in their original rectangular shapes to get a cozier platform bed frame, if you really want to create a custom look or version of your bed then dismantle the pallet boards to get a big collection of separated and removed slats and then plan what every you want with them as they will be used as a unit for either construction of your bed frame!
Pallet boards come in different wooden tones and wooden natures which may be based on their past condition under which those pallets have been treated so they may be just like new wood, rustic and weathered with patina or some time ultra-rustic or in between! You can give your first priority to shipping areas to get any wood nature of pallets as there is always abundance of retired pallet skids and you can choose your favorite one with great ease! And the good news which is above all, is that pallets are totally free to get and hopefully will always be!!!