Throw a Potion of Lingering (Luck in the Screenshots) and you will see that they have a normal Splash Potion Texture.
I think they should have their own testure.
MC-91745
Throwed Lingering Potions are look like a Splash Potion.
Resolved
Duplicate
0
Zaliku
(Unassigned)
Unconfirmed
Minecraft 15w44b
Retrieved
Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-85835. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.