Problem: What are the most important words?
A yellow fire hydrant on curb with leaves and mulch surrounding it.
Answer: hydrant, mulch, surround

Problem: What are the most important words?
biological species in the snow taken under controlled conditions
Answer: condition, control, snow, specie, take

Problem: What are the most important words?
wall painting depicting the birth of builder in a chapel
Answer:
birth, builder, painting