Yes posting photos that don't belong to you and citing the source is still copyright infringement. Most of copyright notice has this in their text:
"All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher"
Copying and pasting photos and citing the source falls under infringement of the owner/author's right to DISTRIBUTE. It is even worse if you cite the source because it basically shows that the images are not yours.
Being a coloring book artist I have seen several people got slapped with cease and desist notice (or even getting sued) for distributing coloring pages without the author's consent.