Okay, I've looked in a couple of other things: Firstly, the piece of software I was looking for was called "Winter". It's a pretty powerful extension, but I doubt Wikia (or any other wikifarms, for that matter) would instal it.

Second, I've found one plausible easier method of plotting; it's called Plotter, and it's currently in beta. It requires the use of JavaScript in the MediaWiki namespace, which would make it pretty hard for the casual user. Plus, it's hard to interact with WikiMarkup both directions that way - many other more generic JavaScript-related extensions suffer from the same problem.

I've searched through practically all the extensions in the Extension Matrix (a large list of basically all respectable extensions).
I've found a possible wiki to try this on: the Fractal Art Wiki, at
http://fractal.wikia.com/wiki/Fractal_Art_Wiki. It's totally dead. I asked an admin to send in a request for DPL; if he doesn't soon, I will.
Here's some possible code I was thinking about for producing the final image:
Template:Plot_Fractal
{{#dpl:
format={¦ \n,²{#dpl:format=²{1x¦}²-,²{1x¦}² style="height: 1px; width: 1px; padding: 0px; bgcolor: ²{1x|²}²{ {{{ColorForm}}} |²{1x|²}²{ {{{NumForm}}} ²{1x¦}² {{{Iter}}} ²{1x¦}² {{{NumParam}}} ,}²{1x|²}² ²{1x¦}² {{{ColorParam}}} }²{1x|²}²",|include={Values}.dpl, ,}² \n,¦}
include={Values}.dpl
}}
This code won't work, partly because I haven't quite figured out how to return just a range of values (although this can be done). Also, I'm pretty sure I din't escape the character correctly. Basically what I'm trying to achieve here is to make two nested dpl calls; the outer one creates a list of lines, the inner, a list of pixels. The outer one adds some value of {Values}.dpl after a comma, the inner one a different set of values before the comma. Then "ColorForm", a chosen name of template which contains the color formula, does operations on NumForm, which does operations using the Iter parameter, the NumParam parameter (which is a comma separated list of values to give parameters) and the pixel value. This code has nothing for page selection right now, and so won't produce any pixels. This is something I still need to figure out.

All help will much appreciated!