Providing excellent keywords with your content is critical to helping customers discover your work. Great keywords are detailed and precise. They relate directly to what is in the image or clip, either by describing what it shows, or what it might represent. For example a photo of a flower can include keywords like yellow, tulip, flower, beauty, spring, fresh.
Photo by mythjaThe overuse of repeated words or phrases in your keywords is not permitted. Keywords with unnecessarily repeated words or phrases are considered spam, and are not accepted for publishing during our review process. Editing keywords to contain unnecessarily repeated words after your content has been published is also not allowed.
Spammy keywords contain the same word or word stem multiple times. However, not all repeated words are prohibited.
Photo by Dean Fikarsunset, mountains, autumn, fall, aspens, fall colors, red, stormy sky, new mexico, fall foliage, yellow, orange, dusk, twilight, sun, purple, colors, colorful, places
The use of irrelevant keywords is also considered spamming. Your keywords should relate directly to the content they describe, either literally or figuratively.
You may want to review these helpful links:
Maximize Your Visibility: Keyword and Title Best Practices
Why was my content rejected for Keywords?