RealWorld Paint is an free portable image/photo/animation editor. It supports layers with styles and can import and export Photoshop, GIMP and Paint.net images with layers.
There are all usual drawing tools and some specialized tools for photo retouching like Clone, Crop with perspective correction, Red eye remover or Liquify equivalent.
Animated GIFs can be created, edited and optimized.
There are downloadable media packs and plug-ins and RWPaint can use Photoshops .8bf image filters for yet more flexibility.
