GIMP is a multiplatform photo manipulation tool.
Vector drawing tool with shapes defined by points that can be shared with other shapes.
Removes superfluous information reducing the size of SVG files
SVG Optimizer / Cleaner
Lightweight lossless file minifier/optimizer.
Tool for optimizing SVG files
A radically new digital design tool built for cross-functional product teams
Online photo editor, which can work with PSD, XCF and Sketch files (Photoshop, Gimp and Sketch App).
InsightPoint is a cool multi-scene vector drawing tool for Windows and Linux.
PicMonkey is a feature-rich online photo editor that works right in your browser; no downloads...
Single-user mockup / wireframing / diagramming tool
A simple vector illustration tool.