This site has struggled for a very long time over raw idea generation. There can be no best answer for raw idea generation. The OP is asking for the proverbial spaghetti to be thrown against the wall so he/she can overcome creator's block. Unless something has changed in the last year, asking for an infinite list of things (a question that is poorly bounded) is off-topic, but asking for a finite list of things (a question is well bounded) is on-topic.
Part of the problem is that even a finite list of things breaks Stack Exchange's basic premise that a well-asked and specific question will have a single best-answer.
Nevertheless, well-bounded idea generation can be as valuable to the many visitors to this site as any specifically-answerable question. Therefore, to remove the ambiguity around whether or not a question should be considered an idea-generation question, I therefore propose a new tag.
Popup
A survey question asks for a list response without expectation of a best-answer selection. Survey questions are required to be finite in nature (see "Catalog of Question Types" - "Finite List of Things" in Meta), meaning they are well-bounded with conditions, limitations, definitions, and specifications.
Wiki
A survey question asks for a list response. The list may take the form of one answer expressing a list, many answers each expressing one item on the list, or a combination of the two. Survey questions are not expected to have a best answer and respondents answer knowing no such choice may ever be made. This tag is not a license to seek unlimited or unbounded raw idea generation.
Survey questions are required to be finite in nature (vs. infinite in nature, which is off-topic), meaning they are well-bounded with conditions, limitations, definitions, and specifications that keep answers focused on the particular problem proposed in the question. In this case, survey questions may be held to a higher expectation of specificity than other questions. As a general example, "How can I..." and "What would happen if..." questions are frequently poor survey questions as they are often too broad and very poorly defined. On the other hand, Vesrei's question "Fauna evolved to use portals" is reasonably well bounded and an example of a suitable question for this tag.
The survey-question tag is not a license to seek unlimited or unbounded raw idea generation. It will be considered abuse to use this tag when asking a question that should have but one best answer in an effort to cause a greater number of answers to be posted. Users are responsible for respecting the difference between seeking a bounded list and seeking a best choice. This tag does not abrogate the user's responsibility to understand how to ask a good question as defined in the Help Center.
Similar Tags on Other Stacks
Relevant Meta Discussions:
- Should we rename Idea Generation? (this is about the old VTC reason)
- https://worldbuilding.meta.stackexchange.com/a/7289/40609
- Idea Generation in Help
- What's wrong with "idea generation" questions?
- Being more up front about idea generation
- Opinion on questions that involve 'idea generation' or lack a 'right answer'
Alternative View Point
Although I'm recommending the creation of this tag, I respect the fact that we may suddenly see 90% of questions using it because people think it will produce a higher quantity of answers — not realizing that the consequence (because the question was not framed for the purpose of a list) is lower quality answers. From this perspective, the presence of the tag has the potential of causing more problems than it solves. If you believe this to be the case, you should down vote this recommendation.
Answers
Ideally, answers to this post should posit issues in support of, or in opposition to, this recommendation to help site users better understand the consequences of this tag. Discussions seeking clarification about the use or abuse of the tag should be in comments.
