For a fan fiction that you submit apps towards, what makes you want to submit an app and read?
What sort of things draw your eye when you look at prospective fan fictions?
What makes you want to read a fan fiction?
I've seen many adequate fan fictions die from lack of interest. Some really good authors don't let the lack of attention and persist writing (my kudos to them). I just want to see what the community would like to see in fan fictions, maybe help boost the readership and lower the death rate for fan fictions (can't remember any that actually survived until the end).
A solid plotline, to be sure, and what you mentioned.
What helps is something that extends or drives Spiral Knights to a more in-depth level, bringing characters to life when in-game, the interactions are actually very dry. Live characters, good imagery, and an engaging world makes reading an adventure. Writing a good story in general that could function on its own as a standalone is the standard needed for most fanficts today.