Most of theses frogs are based on the SVGs of the twitter emoji set (https://twemoji.twitter.com). Others are unique designs with other inspirations in mind.
By contributing you agree to license your contribution under the terms of the GPLv3 (for code) and CC-BY 4.0 (for graphics) licenses. The corresponding license can be found in the LICENCE and LICENSE-GRAPHICS file respectively. The following links also reference to the licenses:
-s, --specific S [S ...] Generate PNGs for each S in the "svg" folder. The '.svg' suffix is optional.
-r, --resolution R [R ...] Custom resolutions that will be generated instead of the defaults.
-g, --git Generates PNGs of SVGs that changed since last auto tag and creates a git commit with them. Requires 'git' to be installed and located in PATH.