I am putting together a study that attempts to assess whether people assign particular affective or emotional states to images--specifically, animated GIFs. Is there a "standard" list of emotional states that has been used in research before, or that tends to be favored by researchers who study emotions? I'm considering something like Plutchik's three-dimensional circumplex model, but I didn't know if there was something else that tended to be more favored.
There are a range of "adjective checklists" that have been developed to assess affective states, personality traits, or characteristics of individuals. Two of the most widely cited measures are the Multiple Affective Adjective Check List (MAACL) and the Multiple Affective Adjective Checklist-Revised (MAACL-R) (Zuckerman & Lubin, 1965; Zuckerman & Lubin, 1985). Although the actual MAACL-R manual may require purchase, lists of the affective items are available in other publications (Gotlib & Meyer, 1986).
Clinically, I have used the How Do I Feel Right Now? chart for clients who have difficulty identifying and naming their emotional states (http://blogs.oregonstate.edu/careerservices/2012/11/30/emotional-intelligence-what-is-it-and-why-do-employers-want-emotionally-intelligent-employees/).
Other sources of emotion lists in the field of psychology include:
Gotlib, I. H., & Meyer, J. P. (1986). Factor analysis of the Multiple Affect Adjective Check List: A separation of positive and negative affect. Journal Of Personality And Social Psychology, 50(6), 1161-1165. doi:10.1037/0022-3522.214.171.1241
Shaver, P., Schwartz, J., Kirson, D., & O'connor, C. (1987). Emotion knowledge: further exploration of a prototype approach. Journal of Personality and Social Psychology, 52(6), 1061.
Zentner, M., Grandjean, D., & Scherer, K. R. (2008). Emotions evoked by the sound of music: Characterization, classification, and measurement. Emotion, 8(4), 494-521. doi:10.1037/1528-35126.96.36.1994
Zuckerman, M., & Lubin, B. (1985). Manual for the MAACL-R: The Multiple Affect Adjetive Check List Revised. Educational and Industrial Testing Service.
Zuckerman, M., & Lubin, B. (1965). The Multiple Affect Adjective Checklist (MAACL).
We are far from having any standards on the topic of emotions, and there are numerous ways to gather a user's emotional feedback. Of course, there is no optimal solution, and the choice mostly depends of your protocol requirements and expectations.
Using emotional terms, for instance, might be limited, as there is a bias of common understanding by every users, and a bias of granularity due to the terms categorization.
However, if you look for a quite comprehensive list of emotional terms, I would invite you to check this list of related terms of the Geneva Emotion Research Group. Other relevant research material is also available from their website.