1. GIMP is a multiplatform photo manipulation tool.

  2. Vector drawing tool with shapes defined by points that can be shared with other shapes.

  3. Removes superfluous information reducing the size of SVG files

  4. SVG Optimizer / Cleaner

  5. Lightweight lossless file minifier/optimizer.

  6. Tool for optimizing SVG files

  7. A radically new digital design tool built for cross-functional product teams

  8. Online photo editor, which can work with PSD, XCF and Sketch files (Photoshop, Gimp and Sketch App).

  9. InsightPoint is a cool multi-scene vector drawing tool for Windows and Linux.

  10. PicMonkey is a feature-rich online photo editor that works right in your browser; no downloads...

  11. Single-user mockup / wireframing / diagramming tool

  12. A simple vector illustration tool.