Girl Genius (first comic) is a webcomic by Phil and Kaja Foglio, of various geek comic (and Magic art) fame. It's also one of my most beloved comics, being about a faux-18th/19th century where MAD SCIENCE rules Europa (and the rest of the world, but we haven't seen any of that), which contains a sunken Britannia, the Wulfenbach Empire keeping the peace with the iron fist and a whole lot of mad scientists (sparks) and other freaks of nature ("An abomination of science that CURDLES THE MILK OF ALL HONEST MEN!" "Well, aren't we all?" "Oh, I SAY, sir!"). But apart from all that, and the amazon princesses, pirate queens, dark secrets, darker secrets, and the mystery of Airman Higgs, what's important is that Agatha currently has 2 beaus. One is Gilgamesh Wulfenbach and the other is Tarvek Stormvoraus, rivals and both scions of mighty empires and/or secret conspiracies. As the links make clear, they both have their qualities, but Gil still remains the favourite.
However, what I hope for is that she'll end up with both. And not one after the other, both at the same time. Why am I hoping for polyamory here? Because it's not really the type of relationship that shows up a lot in even slightly mainstream fiction (and given the number of Hugos Girl Genius has received (three in a row, before taking themselves out of the running) it's... sort of mainstream?), and more importantly, there is a non-trivial chance that it will happen! Why would I expect it from the Foglios? One, the possibility has been acknowledged in the comic itself. Second, the characters aren't tearing their hair excessively about various entanglements (which makes sense since she's not actually in a relationship with either of them yet) which gives some hope that whatever relationship she will end up in will be a healthy one. Third, Phil Foglio wrote XXXenophile, which, as the name might hint at, is an erotic comic. More importantly, it's an erotic comic that is sex-positive, and includes pretty much any consensual relationship configuration you can think of.
In addition, since the characters are pretty much equals and respect each other (and the authors seem to respect them), it would most likely be a positive depiction of a polyamorous relationship between equal partners. And though a webcomic (it's also available in physical form) isn't the grandest of stages, every little step helps.