Are you looking for ideas for all weather indoor type or just mainly spring/summer/fall washing? We have a very simple set up, but it works for the horses, goats, calves, heifers, mature bulls, etc. It is just a large pen under a south facing lean-to (about 20x 10 feet). Concrete nonslip floor and heavy duty panel gates hung (always have lots of extra chain and snaps around to modify the setup). Water supply is piped in across the main barn and hooked to a good pump to increase pressure. It is well lit with overhead flood lights separate from the main barn, has electrical hook-ups in case we need to use it as a clipping area, and mesh to drop down over the south face if it is too sunny. We can use this area to pen wash any bulls that are not broke to lead before our open house in the spring, rinse down 2 or 3 horses at a time after a hard day, or drag in a steel Sullivan's blocking chute to wash an unbroke calf. We also drag in the goat stands to wash bucks after breeding season or does before show time. Like I said, very basic, but with all of the different species we have and tasks to do, it doesn't pay for us to have an area dedicated to say just show heifers, that doesn't work well for everything else too. We also just need a "washrack during warm months, so we can use it for other things during the winter, like a back-up calving pen, storm shelter for a 30 year old gelding for the night, hay/ straw storage, etc.