Yes, this seems like an excellent idea.
I recommend that this have multiple answers, one per application. Each answer can have the Ubuntu flavor and application at the top. For example:
GNOME/Unity (regular Ubuntu) — gnome-screenshot
Ordinarily, you would press PrtScr to take a screenshot.
This runs the
gnome-screenshot utility. However, you can launch it
manually with command-line arguments specifying how long you want it
to wait before it takes the screenshot.
In either the Run command textbox (Alt+F2) or
a Terminal ...
This is just an example. I don't actually know if
gnome-screenshot -d is the best/easiest way.
There should certainly be answers for all the official Ubuntu flavors' default screenshot utilities. But I don't think it needs to be limited to that. Some other applications--or at least one--may be covered.
In particular, in addition to answers for gnome-screenshot, KSnapshot, scrot, and xfce4-screenshooter, I think we should have one for GIMP. This popular program is very good for taking screenshots because it is versatile and powerful (though not lightweight, compared to pure screenshot utilities), and often one wishes to edit a screenshot immediately after taking it.
(If you post this question, I'd be pleased to write the GIMP answer.)
Why This Question Would Be Constructive
In response to concern that this would be considered a list question and closed:
"How to do X?" questions are not list questions. We have many good questions with multiple answers, where different answers apply to (and are marked as relating to) different Ubuntu releases or flavors, or different general kinds of technique (e.g., GUI vs. command-line).
Several of those even have indexes of answers by version in the question, and are considered perfectly good!
Furthermore--while "How to take a delayed screenshot?" would not be a list question--list questions are not actually considered bad. Big list questions, where there could be an unlimited number of answers that cannot be maintained or meaningfully compared to one another, are bad. Here are some open "small" list questions that are perfectly good--or at least highly tolerated:
And there are even some questions with a potentially unlimited number of answers, that are considered good, because they are not lists of software, but rather of methods and techniques (and so are similar to a question that just happens to have a lot of answers):
At exactly what point a list question becomes a big list question and is subject to closure is a little fuzzy, and I'm sure there's disagreement over where the threshold should be set for that. But asking for methods to take a delayed screenshot is quite specific; that is not a big list question.
Furthermore, even if you plan to add an answer index to the question, you don't have to actually say, "one program/technique per answer please." Instead, ask the question and post whatever answers you want.
If you've already posted an answer and want to split it into multiple answers, that's fast. (All, or all but one, should probably be community wiki. Please note that you don't need the assistance of a moderator to make an answer CW.)
If you're first writing the question, click the checkbox for answering your own question, and compose at least one of the answers. You can actually compose them together (benefiting from the formatted preview), then separate each section into a separate plaintext document on your computer (make sure to convey any corresponding link/image URLs from the bottom of the answer, to whichever document they correspond to). Then you can have one answer posted immediately, and the others posted in well under a minute.
This has the advantage of showing people the benefit of having one flavor/application per answer. If they want to break with that format, that's fine! This fineness is an important indicator that your question is appropriate, and not a "big list" question.
By the same token, if you've posted your question and posted an answer covering multiple applications, and you don't want to split it, that really is fine too.