Hmm, no, this isn't limited to Axel route, it happens also if Lena chooses option to take a selfie, and likely on all other routes, seeing how the relevant block is copy/pasted in all branches:
Python:
scene v14_pool_selfie_bg
if v14_topless < 1:
if lena_bikini == 1:
show v14_pool_selfie_bg1
elif lena_bikini == 2:
show v14_pool_selfie_bg2
elif lena_bikini == 3:
show v14_pool_selfie_bg3
if lena_smoke:
show v14_pool_selfie_bg_smoke
show v14_pool_selfie
Effectively, game only shows the last variant which is Lena topless. All others (the ones with _bg extension, including the _smoke one) are not defined, so they don't have any effect (and if they did, if the image is not composite then with how this block is structured, they'd likely get obstructed by the final topless image anyway)