We have a gooseneck trailer with a "weekend" package in the front - bed, microwave, seating, closet, etc. But we have also camped in tents near an old style BP trailer, and packed a small dome tent onto the trail.
Here are my list of favs for at the trailhead:
Solar Shower Unit. These come in sizes of 2.5-appx 4 gal size with a sturdy pvc handle, rope attached and long nozzle for showering. They can be layed out - black side down/clear side up - in the sunshine for part of the day and you'll have a nice warm or hot shower waiting at the end of the ride. This is hung in the back of a horse trailer. We had this for a long time. The only draw back is if there really ISN'T much or any sun and it's cool out - the water will not heat. Cost: appx $12-18 depending on size, brand and merchant.
A Zodi Hot Water Unit. This is a 4gal stainless steel tank that you heat with a little propane cylander burner unit it comes with. It is pressurized by pumping it just a few times and has a nice long shower hose nozzle attached so you can hang the nozzle above you for the shower. Some of the other hot water units require electricity or huge battery packs or 12v batteries to be hooked up - hassle! This runs around $100 depending on sales and merchants. The others were closer to $150-200. We set this up in the back of the trailer. You do need the small propane cylanders to heat but they do not use a lot of propane to heat the water so one goes a long ways. We always keep a min of 3 in the trailer. Those are cheap enough on sale -
For those who are not fond of hanging their rear over unknown plant life to "go" - a nice molded toilet seat unit that fits on any 5gal bucket with a kitchen sized trash bag installed. Nothing left in the wilderness - this is also set up in the back of the trailer - dispose of waste properly when you go home. Price for seat: $12-15
Portable corrall electric or non electric: We found a number of commercially packaged "kits" out there for electric corrall units ranging in price from $159 - $290. Of course, if a person has a horse/horses that are very respectful of fencing, the fencer is not required and any rigged unit will work with items like ribbon, wire, webbing, etc, and some sort of posts. We managed to put together our own "kit" at a good price when we went out to find a really decent little battery powered (D Cell) fencer for very little (about $40)
http://www.horse.com/Battery-Powered-Portable-Fence-Charger-BXW12.html and bought a 250 foot spool of the electric fencing twisted rope (about $16) or up to around 650 ft for $29
http://www.horse.com/Sure-Corral-Poly-Wire-Fencing-BXL04.html along with poly step in posts at $1.99 each. We purchased a large/long sports duffle bag to carry the whole package at $6. With this, we were able to put together a system that costs less than $90 depending on merchant and location. This item is really great to have with in areas that allow it - check to be sure it is allowed to corrall in the trailhead area you are camping.
Webber Q Baby Grill. $179. Yeah! I love this grill. It's a table top grill model but packs a big punch in how well it works, cleans up and space. It has a nice large cooking area - two "wings" that fold out on each side for prep items, heavy duty cast iron grates and an electronic ignition. Press the button and it's ON. Heats evenly and fast. The lid stays on tightly to hold the heat in, it is pretty fair in staying lit with breezy locations - not perfect but better than any other table top grills we have had. Nice grill - got it for my bday from DH for the horse trailer and love this item.
Honda generator: The little Honda 3000 does a supurb job of operating almost anything your trailer, camp or tent needs to run on electricity and it does it SO quietly you can't tell it's going. These are approved by Federal and State campgrounds nationwide to be within the 60db noise level. They are actually less than that so your neighbors and horses will appreciate that. It is also pretty darn efficient on using the fuel so you won't have to haul multiple large gas cans with to keep it powered. We don't run it often, but occassionally to heat the trailer with the little ceramic heater, run a microwave in the trailer, Mr. Coffee, etc. It's nice to have IF you need it.
For those who like them: Marguerita in a Bucket. Coolest and handiest thing. They come in traditional (plain) or Strawberry. Just add your fav tequilla, or don't for those who do not imbibe -it's still good, and chill to serve over ice with the built in spout OR put into the freezer to scoop out for frozen Margs or mix up frozen mixture until it moves enough and can flow out of the spout. This is what we do - freeze, then use one of those little hand held mixers/blender units to get it smooth, then pour out the spout for nice frozen strawberry Margs. Yummie around the campfire at night.
We like to bring with a portable fire ring. They come in all sorts of sizes and designs - some pre-fabbed units with the designs lazer cut into them like deer or horses, pine trees, whatever. You can also bring or find a stack of nice large rocks to contain your fire ring or purchase the big retaining wall blocks - two layers of those make a nice fire ring. Be sure that fire is OUT - douse it good - before going to bed or leaving the site.