Roundabout technical evidence to me is a slippery slope that should be avoided.
Quick thoughts.
Why is the water slightly green? Algae.
Evidence of organism
Why does the rock have some discoloration of yellows and blacks? Lichen.
Evidence of organism
Why does the ground have a brown substance called dirt? Dead organic matter.
Evidence of organism
Why does the atmosphere have oxygen?
Evidence of organism
Pink lawn flamingo made by a person.
Evidence of organism
Really if you try hard enough and have a trained eye, you could argue evidence of organisms from nearly any photo.