I understand the restrictions on covers, or at least the reasoning behind them -- oekaki is for oekaki. It's a forum for a specific purpose, even if it has a built-in art program. I can't go into C$ trades and make a post about my favorite video games, because the thread would be moved or locked.
And I do prefer having any frame of reference (like we now have) for covers over none, so I can avoid accidentally breaking rules n getting threads locked.
However the rules are a little confusing. In theory I think they work, but the more I think about it, the more questions I end up having. Probably overthinking this, but hey!
I did a few quick doodles, so the post will be long, but I TRIED to make images small I promise XD I know staff can't plan ahead for every possible contingency, but I hope I can at least more easily convey my questions this way.
The point of most of the following questions: at what point is a cover 'done enough,' as it were?
let's say I have an adoptable. doodled this cat-thing up in a few minutes to act as a model for us, vaguely based on sweet treats (please ignore the fact that in subsequent images I forgot to give it a nose :sob:) :

the following two are unacceptable as covers, as I understand it. Neither took me a long time (or a lot of effort) to make. The first one took maybe two minutes, and the second one is just a more clean version of that first color-less sketch.

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would these following two be acceptable, though? I feel like they probably would be, but I'm not sure.
these were not hard to make. they didn't exceed ten minutes in their creation (probably took about five max), and are just colored-in versions of the "cleaned up" sketch. if I were describing these to someone, I would label these "sketches" or "doodles," even if they are both colored and one even has shading. This is about the effort I put into character meme redraws for myself and friends.
though they have more effort put into them than the sketches above... they aren't what I consider to be my usual standard. this doesn't mean these would be fast sketches or low-effort for
every single artist. For me, this is a sketch and something I can do in five minutes. For someone else, this might be a
twenty-five minute headshot. I need to be clear that this isn't a dig -- there are plenty of skilled oekaki artists that post what they personally call "sketches" that I know would take me an hour or two to replicate, if I even could.
But then I have to wonder how exactly a sketch is defined (uncolored-in lineart with clear construction lines?), because this is my "lazy" art. The art you are looking at now did not take much effort.

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this one is properly lined, colored, and shaded. Lines are shaky but my lines are pretty much always shaky lol. I'm fairly certain this would pass the cover check. It didn't take me long, sure, but I put more work into it than the others.

but then what about this? it has neat lines and is shaded, and the colors are similar to the adopt but it's not actually fully colored like the adopt (sort of just filled-in). is this acceptable? Not?

Or if the adopt cover is accurately colored in, but messily? Is slapdash coloring enough to tip something into an inappropriate spam cover?

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then we have covers that aren't the adoptable itself. would the following be an acceptable cover? the adopt is based on desserts, but nothing in particular, and it's not a direct connection (the cat-thing doesn't have cake frosting on it, for example).
The cake isn't an "accessory" or their favorite food or something; it's not world or character building for the adopt. This is a somewhat common style of cover (more often seen in closed species I think) to create an item that abstractly conveys the idea of the adopt.
I would not consider this worldbuilding for the adoptable, and it's clearly not the cat-thing itself, but it's not entirely unrelated to the adopt either. Is this allowed? Disallowed?

Then for actual accessories: do they need a certain level of polish past not being no-color sketches?
While I know the collar on the right would likely be fine as a cover, would the left one be? I want to say yes, but I'm not certain. Drawing a collar doesn't take me a lot of time, though it's definitely related to our theoretical adoptable, since they're wearing it!

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I think most of the images here would count as acceptable covers, and this feels like a long post and very worthy of a TL;DR.
But I have to ask because this is meant to combat spam and "low-effort" covers made to post off-oekaki adopts on oekaki, and I wanna know what falls under that definition D:
It's not like i'm trying to get around the rules, to be clear -- but there are some covers that fall between 'clean headshot' and 'construction linework,' and I want to know at approximately what point that line is so myself and others don't trip on it accidentally. I myself have done a number of these through the years!
i think i'm overthinking this.