Skin slots in the Dressing Room are taken up by a loading icon which does not go away. Attempting to create or edit these skin slots fails, as it sends you to your last equipped skin slot. These infinitely loading slots are rendered useless and the created or 'dressed up' skins inside them are effectively lost.
This bug persists after reloading, relogging, and redownloading the game. It also persists without custom skins, skin packs, or resource packs.

The bug has also affected many others within the past 1-2 weeks:
https://www.reddit.com/r/Minecraft/comments/1ciwb90/my_skins_wont_load_on_the_bedrock_dressing_room/
https://www.minecraftforum.net/forums/support/minecraft-bedrock-support/3199122-minecraft-skin-cant-load-at-all
https://www.reddit.com/r/Minecraft/comments/1ccmzhe/all_bedrock_skin_slots_bricked_infinitely_loading/

From past "resolved" bug reports, it seems like a similar bug has happened before and fixed itself, but this is a new, recent issue experienced by many.

Additionally, I believe that this bug is the cause of an error message I get when joining a featured server: "Appearance is taking a long time to load, proceeding with world generation." After this message flashes on screen for a split second, the server will load but I will have a default skin (Steve/Alex) instead of my custom skin or skin from a skin pack.

appearanceTookTooLong.mp4