The character skins created via the in game created are often not loaded to be seen by another players. This can be temporary fixed by entering Profile -> Character edit -> Classic skins and turning the skin back on. I'm playing on a shared World by one of the friends on Windows 10 Edition. Players that are currently nearby see the skin again after using the mentioned method but only for some time but other players do not. The player on the screenshot is currently using the rosebush skin from Bloom pack but on my side he is seen as Steve.