Could you explain what you mean by "the old textures remain in the scene", and "(the scene) still has the ... textures attached"?

I'm not questioning what you are seeing, just trying to work out the precise meaning of your words.

Presumably there is nothing in the scene that is still using the old textures, since you deleted those objects, or applied different materials to them. So where are you seeing the old textures in the scene?

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)