Why are these skins so difficult to imagine?
Bandito was already lightly lumped into the same universe as High Noon, and given that Fiddle is a demon now, that's just a complete shoe in to the skin line now.
Fiddle Me Timbers will still probably be lighthearted, or at least more "Pirates of the Carribean." Skins are intended to apply different feels to champions, and a pirate skin can be a lot of fun. It can fit well with things like Bilgewater Swain and Katarina. I don't think there's any reason to shove it into Dark Water or Fables since it doesn't share thematics with either.
Surprise Party will still be surprise party? Of all of these skins, the one skin he's got that is focused around SURPRISE shouldn't be too hard to imagine on a champion who's new forte is bursting out of nowhere and scaring the shit out of you. It's intended to be a goofy skin, like all of the other Surprise Party/ April Fool's skins. It doesn't have to be a die-hard horror story skin because it's not trying to be.
UNION JACK IS NOT ANYTHING LIKE CRIMSON AKALI. Crimson Akali was a throwaway garbage recolor skin. Union Jack was a skin released to commemorate one of the Olympics years ago, with skins like Whistler Twitch for Germany, and that Amumu skin, The USA Anivia, and a Tobaggan Corki, and Curling Veigar, etc. It's got a solid thematic it can stick to, even if it's currently a poor recolor - unlike Crimson Akali which was nothing but a red Akali. It will be updated to fit it's Olympic theme, just like Twitch's skin was.
https://ddragon.leagueoflegends.com/cdn/img/champion/splash/Twitch_2.jpg