Strange thing is happening for me : the gender icon shows in the members list, but nowhere else. I checked 3 times if I properly edited the postbit_legacy and the memberlist_resultsbit, and it seems to be ok. I also checked the .gif names (if the matched with the profile field), and it's also fine. That's weird...
Edit : problem fixed. I had to put avatars/usernames/age/... to the left :
Admin CP > vBulletin Options > Style & Language Settings; and set the "Use Legacy (Vertical) Postbit Template" to Yes (and save)
And now the gender icons show up.