To gain understanding about copyright, check the bottom.
1) We shall not accept any copy or traced work from official art work (especially copying a picture that is from something like an anime fanbook/artbook or a screenshot). And no, just linking back to the original source is not enough.
2) We will not accept anything that had used screenshots in the deviation in any way.
Copied and traced work is still plagiarism and people have gotten in trouble for it. (It's the art version of plagiarizing from another person's essay or even from your own essay sources. Hence, the reason why MLA is very important...not just for school but also for life and to protect you from the law.) They are NOT fanart.
What is acceptable is to go through dAPoses or another stock club for whatever thing you need, read the stock artist's rules (only of the stock artist that you chose for the meantime), use the stock to help you get the pose down then turn that pose to whatever character you wish. That is standard for millions of people. (I am in awe with those people that can draw using their mind 100%...but that must have taken tons of training...)
However, if you wanna post your copies and traced work...the admin says it's okay to even put them in the scraps. Deviants themselves have said...put them elsewhere....or just keep them to yourself.
You can learn from copying and tracing work. That is actually true. Copying and tracing can be very helpful. (There are even teachers that says this and people have been able to 'see through another set of eyes' due to this and have even improved in their other interests.) However, what I would do is keep them private. Think of copying and tracing just a step... like a presketch...not in any way a final result.
Screenshots is also a similar case. You can get in major trouble just be using official work even if it's a collage wallpaper. (Seriously, collages has always been an iffy part in art in general.) Actually, even if you create something using a generator, that can be a problem. If it's a face generator, keep it in scraps since the character is still yours.
This pretty much applies to all genres and art forms. Just linking back is clearly not enough. People can sue you even if you link the source. Actually, putting up the source makes it more readily to be taken down. I'll explain.
Always ask for permission if you WANT TO reproduce a picture you don't own for practice AND WANT TO SHOW YOUR WORK OFF even if it's NOT for commercial use. Otherwise, it's still considered stealing.
a) Instead, you can always take the picture yourself.
b) Personally, I rather go through stock first. They have rules you can read which covers 'getting the permission' part because the answer would be there already and since stock is made to be used by other artists. If you don't get the answer in their rules, ask them. They make their stock TO IMPROVE YOUR ART.
You may get yes and you may get no. There are people that LOVES THE BIG COPYRIGHT and there are people that LOVES THE CREATIVE COMMONS.
People who say no even for NON COMMERCIAL uses would probably be the BIG C (COPYRIGHT) people. Even if you reproduce, release it online, link the source...you can still get sued for not asking for permission.
Actually, for the big companies, it's probably better to avoid though because their a big business compared to where you maybe one person. You can e-mail but whether they will read it is perhaps another question. And since they're a big company, they can sue you for thousands of dollars. You don't wanna get into debt that way. (Hehe...the maybe cost of another four (or eight) more years of college at least that you can't even get anything out of it from....) I know that can be the cost of merely stealing a song...and that's just for non-commercial use. And don't think that 'they have not complained' covers it either. What happens if they actually discovers it? And dA probably will not even help you if you are in big trouble.
Then there are people, like myself, that likes creative commons. They say yes for non-commercial uses. You may actually not see creative commons around but asking permission can be a big difference. Actually, even for artists that may say yes, they may not like it if you skip asking permission in the beginning. Learn more about creative commons here... creativecommons.org/
And sadly, this site is an American site. As long as you're here, it's like you're in the United States. You must follow our rules even if your country follows a different set.