This guide should be helpful to explain which kind of render is accepted on the site and which are not. Plus, there will be some tips on it then you can avoid the fact that your creations will be deactivated.
To start, a little lesson of vocabulary should be useful.
A lineart : is the outline of a
drawing. This one can be done to be coloried later from the creator or can be free for anyone who wants to color it.
A render : is an image traced from
an official image from an animated movie. This image can be colored by its creator to put the color he/she wants to add.
A blank render : is the outline of a
render. This one is free for anyone who wants to color it.
Another thing that should be helpful is the notion of
paintfriendly. This is a term to define a lineart or a blank render realised in
strong pixels. The goal of those lineart/blank render is to color them easily with paint and so, they are easy to color for the beginners.

Here is a paintfriendly lineart ( your can see the strong pixels which look like little black squares ).

Here is a lineart which is not paintfriendly ( you won't see the little black squares ).
What's accepted on the site :
The good renders.
A good render is a render which is made with care and throughness. The member who made this use fluid lines, a good coloration and don't go out of the lineart and there is no space which is not colored. This is easy to be confused about if they are images from the movies or drawings, because the creators of those render take care of what they are doing. Most of the time, those renders are made with a graphic tablet or with the pen tool. But some members can make them with the mouse or with an Ipad ( or other kind of tablet )
Of course, there is nothing more to say about those renders.
The beginner's renders :
The render from a beginner is not as good as the one from an experimented user. Frequently the outlines are awkward and less fluid but they are still in a good quality. The coloration goes with the outines, this is less precise, sometimes go out of the lines but are still well done. In fact, this kind of renders are made by members who are beginners in images or who are experimented with their program. Most of the time, they are made with graphic tablet and mouse ( Ipad or other tablet ).
Those renders are not perfect, but they are allowed and if you have some advices to give to those members, then they can improve, you can help them as long as you are not rude with them. Don't forget that a good critic is not only about pointing the negative points but also the positives one and the goal is to help, not to hurt.
In the same order, we have the images from the movies which are colored with the painting pot. The painting pot can be a good friend but also an enemy. In this case, the coloration is near from perfect and is then allowed in the site. Even if the quality is not the same as a render, the outines are visible and the image is still easy to recognize.
And to finish with what is allowed on the site, the blank renders/lineart which are well colored. You can see here that there is no white spots between the lineart and the coloration. You have to know that it's easier to color a lineart like this ( which is paint friendly ) with the painting pot. But you can easily color a non-paintfriendly lineart if you can use the layers with your program.
What is not allowed on the site
Bad renders are not allowed on Animation Source. This one is badly made, as been made really quickly, the coloration is wrong and goes out of the lines. Most of the time, they are made with the mouse or with a graphic tablet and they are made quickly to be sent as soon as possible on the site. You have to know that this is useless to rush, those would never been accepted on the site 'cause they are too badly made. To avoid this, take your time and don't try to go too fast when you're making your image. You can also make a zoom on your image, this is easier to trace around the lines.
Unlike the other images colored with the painting pot, this wouldn't be allowed on the site. The coloration is too badly made, we can still see the coloration from the movie and the outlines aren't easy to see. Needless to say that this can be made by anyone in 3 clicks. To avoid those colorations, you can :
- Change the size of your point ( on this image, it's at 10, on the other at 40 )
- Use a brush to make a better coloration.
And finally, the badly made lineart. This is typical from beginners. You have to know that this can be fixed easily with using a paintfriendly lineart like I showed you before. But even with a paintfriendly lineart, you can have white spots. Yes, this happens because the pixels are isolated from the lineart. You just have to use the painting pot on it and they will be colored. But, to go back to the non-paintfriendly lineart, you can :
- Give up and try to find this lineart in a paintfriendly version ( many lineart makers make both ) or just try to change for another lineart.
- Use the layers to color under the lineart.
I hope this will be helpful for you to know what's allowed on the site.