Yonic: Of or pertaining to the yoni; vaginal or sapphic in shape, texture, or color. While caves, full blown roses, pots, tunnels, or wells are said to be commonly yonic, people generally don't point these things out on a day to day basis. That's where an artist might come in and compose some of these images and symbols in a particular way to suggest something sexy. Of course, not all designers or artists are created equal. Some artists might understand a lot about chiaroscuro shading, shape, and colour, but because of their inexperience in other certain areas, they might produce something amusingly yonic.
On the flip side, the double-take at the sight of the brain bug in Starship Troopers, the giant squid in the Watchmen, or the facehugger in Aliens might also illicit amusment, but of a slightly different variety since they suggest that someone knows what they're doing. Of course, sometimes all of this is just in the eye of the beholder, and requires some immaturity. Here's a list primarily dealing with yonic themed imagery on the covers of comics.
http://www.ranker.com/list/the-most-amusingly-yonic-comicbook-covers/switchdoctor,
Avengers Vs. X-Men No. 0 Variant Edition
A striking phoenix pose creating beautiful rebirth imagery...cosmic cootch.
Detective Comics Vol. 1 No. 534
Batman and two other guys inside Poison Ivy's fly trap at the same time...Bruce kicked the third guy out.
Omac Vol 3 No. 3
Congratulations, your heat lamp is crowning.
Grimm Fairy Tales Presents: Wonderland No. 7
Ripping off Botticelli, but swapping his use of the sea shell as a vulva metaphor for...o i c wut u did thar.
The House of Mystery Vol 1 No. 251
One vagina dentata that can do much more than bite off weiners.
G.I. Joe Vs. the Transformers Omnibus: Vol 1 to 4
Here comes the head.
Walt Disney Presents: Winnie-the-Pooh No. 1
Pooh..clinging to a delicious honey pot.
Flash Vol. 2 No. 232
Deep trouble...the Comics Code Authority; labia = bad, incandescent glowing hymen = A-okay.
G.I. Joe Vol. 1 No. 3
Snake Eyes scores!...seems a little messy though.
Little Beaver No. 8
Little Beaver...mere inches from getting pierced with a hot shaft.