What are some alternatives?
When comparing Designtack and Pixlr, you can also consider the following products
Contentdrips - Create micro content for your social media growth
GIMP - GIMP is a multiplatform photo manipulation tool.
Canva - Canva makes design simple for everyone. Create designs for Web or print: blog graphics, presentations, Facebook covers, flyers, posters, invitations and so much more.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.