A gaming miniature usually has a base it stands on so that the miniature doesn't tip over during your game. After you paint a miniature, the finishing touch is to clean up the base, because inevitably paint has splattered on to it as you've been painting. Some people decorate the base with tiny shrubbery, or little rocks and sand, or pipelines and cables. Not me, though. I like my bases stark and simple.
The art of basing is, as far as I know, the logical continuation of the tradition of diorama. You've probably seen it around model train setups. Tiny little houses with tinier little gardens lined up across the edge of an electric train route. The end result is like a painting, but in 3D, and really really small. I think a lot of people, including myself, are fascinated by the idea that you can create a small world that seems full of life, but is frozen in time. I see a diorama, and I want to shrink myself down, press Play, and step into the miniature world. Aside from the circuitry and construction, I think the diorama aspect of model trains is a major part of that hobby's appeal.
Wargames do the same thing, and obviously adds rules to how the miniature world works. Little fortresses tower over miniature soldiers, who roam around among tinier little shrubs and rocks and terrain. If you're the kind of person who spends days constructing a battlefield for your game, then it's only logical that each miniature becomes its own diorama.
That Skiitari miniature you painted ought to be standing on the surface of Mars, with red cracked soil instead of plain black plastic under her mechanical feet. The soldier you painted with an ice theme, though, deserves a snow-covered base. And the drone ought to be on a base that looks like the tile of an high-tech space station. The base becomes part of that character's story.
Conflicting storylines
For me, though, there's a problem. Actually there are two problems. Problem number one is that I don't find it interesting to decorate bases. I don't know whether it's satisfying or not, because I've never done it, but I do know that I've not been compelled to try it. I could be missing out on a great creative outlet, but so far I just haven't been inspired to give it a go.
To be fair, usually after I've finished painting miniatures, I'm so eager to play the game for which I got them in the first place that I can hardly bring myself to clean up the bases, much less decorate them.
The other problem is that I can't imagine playing with a miniature with a base that's inappropriate to the setting. Suppose I'd painted a daemon with a high-tech space station base for a Space Station Zero game, but then wanted to use that daemon in a Reign in Hell campaign. Why would the daemon be standing on the scorched ground of Hell, but have a space station tile under foot?
Suppose I painted a ranger for a Pathfinder game and sprinkled its base with model grass and a tree stump. How do I explain the grass and tree stump when the ranger inevitably wanders into a dungeon? Worse still, what about when the ranger ends up at the bottom of the ocean to hang out with merfolk?
I know, I know. The contents of the base aren't the only thing about miniature game figures that don't make sense during gameplay. My paladin miniature has a sword and shield even in the friendly local tavern. All miniatures are locked into exactly one pose for the whole game. There's so much to disbelieve about a miniature. Still, for whatever reason, I can't get over a mis-matched base.
Baseline storytelling
Admittedly, I don't leave my bases completely "unfinished". I use Citadel's Astrogranite to paint the top of the base (usually to hide paint splotches) and I reinforce the base's black rim with Abaddon Black as needed. That feels suitably all-purpose to me.
I think bases that tell a story are very cool, and creating them takes imagination and talent. I'm not saying I'll never base my miniatures. If I get good enough at painting miniatures that I need an extra challenge, I'll likely start making the base part of the art piece. For now, though, I'm keeping it simple, keeping it basic.
T'au soldiers photo by Seth Kenlon. Creative Commons cc0.