Canva is a DIY graphic design tool. It is free to use website (with premium options) and helps you to create images, business cards, Brochures, Social media images and more.
Adobe Photoshop is powerful image-maniupulation software. It can be used to create website and blog images, edit and retouch photos and many more.
Aviary is an image editor, available for use by individuals and also within apps. It has many feature and filters to use on your images.