You need pics of Dragon's bridge, Wolfwood's bridge, and Wolfwood's and my houses.
Also Demon's nature shack thing.
Oh, and mob spawners can still work. The one I built in my singleplayer works fine, just slow.
Mobs don't spawn within 25 blocks of you in all directions, so the spawning area should start at 25 blocks out from a "central point."
Mobs don't spawn outside of 80 blocks from a player
Within that 160x160 block square, a more or less constant amount of mobs will spawn, so a giant indoor room is more or less necessary to prevent mobs from spawning in caves, where they can't be "utilized."
Water flows prevent spawning from what I can tell, so they should be used sparingly outside of the 50x50 block square, but they should be used to help mobs come closer to the killing section.
My singleplayer spawner:
collection room:
player stands on central point, ladder starting one block up from the floor directly in front of the player
collection room has (6 or 7) spaces to either side of the central point empty
room has two-high glass wall border (i believe on "ring 7" from the player), leaving a space of air above the floor (below the glass) for water to come under
behind the glass wall is a "killing trench." The top 3rd/4th layer of the trench (4 or 5 blocks deep), NOT THE TOP LAYER, is where the water sources are. My trench can't fit spiders, so I use cacti above the trench, but for a new version I would probably try out a two-block wide trench, to drown spiders as well.
Spawning Floor:
You want the spawning floor to be a level above the trench, so that mobs forced into the trench plummet and sink into the trench water, as opposed to gently landing on it and swimming on the surface.
I have two layers of water current to each side of the spawner (I technically only have one side of the spawning floor cleared out...). The first layer of water sources should be on the 8th block, so that the water doesn't flow over the end of the floor and into the trench.
The second layer of water is one block higher, and another 8 blocks back, so that this water flow doesn't flow over the edge, but stops right at the edge of its section.
I believe more monsters spawn deeper under ground, so have the collection room on layer 10ish (so that slimes don't spawn in your room and kill you). I have a feeling that multiple floors would work fine.