Good examples given so far!
Still have to check:
Generation Next # 3
She leaves to check as Vincente drifts out of the Quietus disguise. Once again, he discusses the plan with Husk; he doesn't think that they are going to survive the mission. Husk comforts him as she steps out of her outfit and into the shower.
The Incredible Hulk #408
Marlo takes a shower to get ready for the special night Rick has planned for her. Betty asks Marlo is she remembers anything about when she was "knocked out," not telling Marlo that she was really dead. Marlo says that she really doesn't remember too much except for seeing an ankh.
MJ was clothes in the shower when Pete saw her just before his deal with Mephisto in 545 iirc.
Dont have the issue but it looks like tomb of dracula 67 has a scene:
Not sure if Marlene is naked in the shower in this issue's partial scan here:
And of course What If? #34 doesnt count:
But we do have New Mutants 46 and Hood 2...
What issue was this found panel in? Tsarina is her Russian pet/nick name, right?