I found the way how to display this modern image format in enigma2, well not directly but with the use of ffmpeg, on the PC the conversion is done in a second, I tried it on PLi 8.3 and ffmpeg misses webp codec there, can you try this on PLi develop, I assume ffmpeg is uptodate,if not can you add webp codec please, how long does it take to perform conversion
ffmpeg -y -i sample.webp -vf loop=-1:1 -t 5 sample.mp4
the output is the 5 secs video clip (actually still picture) in mp4 format, if you press pause while viewing you can watch it longer not just 5 secs, you can download some sample files from
WebP-Galerie | Google for Developers