Two thoughts to begin with.
Bigger main pictures.
Most people aren't viewing the wiki on their 2005 iPod Nanos so we can do bigger pictures. Instantly being able to see the pic makes the understanding of what it is 1000 times easier.
For vertical images, like book/comic covers, that aren't in a template box thing, we should use |thumb|400x400px]]
For horizontal images, or images that are only slightly taller than they are wide, we should use |thumb|350x350px]]
Main body images should be |thumb|250x250px]] to |thumb|300x300px]]. Being able to see the pics helps so much.
My second though is about Tags.
We need more consistent tagging. All horses should be tagged with Horses, Animals, and probably Steeds. Lets also make sure all of the Magicians are tagged Magician, all of the magical McGuffins are tagged Artifact and Magic. And so on.
Lets make it easier for people indexing comics, or writers looking for a specific type of thing to add to the upcoming mini comic they're writing, to find the things.
I was indexing the third issue of the London Editions MOTU comic yesterday and it took me longer to figure out the horse Tri-Klops was riding was (a non-robotic) Night Stalker.
What Style Guide changes would you like to see?
Don't link to some other Wiki's style guide and expect me to read and implement it all. Just give me a couple of suggestions.
Last Thought: Blank Pages
I strongly dislike Template pages that are a bunch of headers for information that isn't available or may never apply to the subject of a page.
If there is little to no information available, let's not make people scroll through and read a lot to find out there is no information.