Image Colour Transfer - A free-to-use browser-based application that allows an image to be recoloured to match the colours of another image using novel methods.
Img.vision - Image hosting & video hosting for eCommerce sellers
Colores - Find color palette ideas via image search
UploadHouse - Thumbnail and resize your photos and images
Alembic ⚗️ - A Sketch plugin to extract a color palette from your images
ImageVenue - ImageVenue is a great online hosting service that allows uploading pictures for showing creative works with a simple-to-use technique.