I want to pose a bit too 
Just thought someone might be interested or even a bit inspired. My singleplayer world, using IC2 + Buildcraft + Railcraft + Forestry + Portalgun (well, I have it installed, I'm not "using" it yet) as my main mods.
I want some older industrial feel in my world, and add mods only from time to time (only recently added Railcraft and later Forestry) when I want to try something new. I miss Redpower badly. Thaumcraft and Mystcraft seem very nice, I just didn't try them out yet.
Picture description!
First picture: This is my peninsula. A forest biome about 3/4 surrounded by ocean, which I found quite nice (also I spawned there ^^). I wanted to take things slowly and actually build factory buildings around my machines this time, upgrading and adding new buildings from time to time, to get a "growing settlement" thing going. Buildings, from left to right: Apiarist's house (Forestry bee collection, some machines to process honey + stuff). This was my first workshop with basic IC-machines and generator once, but I converted it recently. In the background - the steel works. Contains Railcraft stuff, coke ovens, blast furnace, rolling machines, boiler... steam-powered, everything for making rails. In front of this: the main workshop. With ore processing facilities, autocrafting grid, and a big vault of chests in the basement beyond. Peeking out behind it are the tanks of the geothermal power plant (BC tanks, didn't have railcraft when I built this). Then - at the front - my beachhouse. The first building I did, just a bed and some storage, also library + enchanting table in the basement. Behind this, a forestry wheat farm. Behind this is my second workshop - it once contained IC- machines, now forestry stuff and a bed if I don't feel like walking to the beach after work To the far right in the background are the barn (some cows and sheep), oh, and before that a cactus farm.
Second picture: The workshops and the geothermal power plant (out of order at the moment). I really like the brick texture, and don't very much like construction foam except the gray ones, but I wanted some color in my world. So I made a custom texture pack using a bit of the Painterly Pack (dirt and grass, also glass and wool) and retextured the CF to be colored bricks. So all the "brick" buildings are actually CF 
Protruding out of the main workshop is the laser lab for buildcraft gates and stuff, since these things are dangerous. Can't have a stray beam cutting any machines inside the main building.. (No, not really. You know, just make-believe ^^).
Third picture: Everything from the other side, to get a better look at the steel works. I really like how this one has turned out. Though the inside needs some work. Moar powah! Oh, and forestry peat bog and tree farm.
Fourth picture: Control floor of the main workshop. Crafting grid galore. Guess I could neaten this one up a bit too, some walkways for maintenance... hmmm. Ah well, admire this mess please. At leat it works good
Fifth and last: Industrial mining with style! I always wanted an excuse to have carts in my mines, and railcraft gives these. A line of miners gets emptied by a chestcart... energy usually got supplied by batbox cart, but it doesn't work now somehow (since IC2 1.107). Guess railcraft has to adapt to the new energynet code first. So geothermal power has to do for now.
Everything is a work in progress of course. The steel works will be getting some nice chimneys for example, and I want to build a biomass power plant and a high speed railway to the next NPC village and the end portal, and a IC farm in the skies over the next swamp biome, and a railway to this of course too, and some IC flower fields (had those but removed them to make room for the wheat farm), and offshore oil rigs and a refinery and ... ah well.
What you didn't see: a reactor in the basement of the main workshop. An automatic subway supply system for all the forestry farms (and semiautomatic for the steel works). And an ugly but effective mob farm in the skies over the ocean. And the upper end of the big black cable leading to the wind power plant. But it's all there, I assure you
I hope you like it! Comments or criticism (or ideas!) below please 