Once all is said, and I've said enough already, I'm a supporter of signatures, as I was of avatars, though I may never get, make, or use one. I try to believe that not everyone on the internet will automatically abuse any or every feature they're privileged with. Though I may just be an optimist.
The thing is, though, that to many people the nature of image sigs is inherently abusive, regardless of what actually goes inside them. There is
no other way anyone could get away with spamming the same image every time they post. None. If I were to put a clever image joke in every post I made normally, I would (quite rightfully) be banned from nearly any forum on the internet, since spamming is a terrible thing regardless of what you decide to spam.
I am not objecting to individual theoretical image sigs, but to the concept of image sigs as a whole. A clever image or tileset or whatever belongs in a thread devoted to it, not in every single thread you post to; people who make good content for DF can post it to an appropriately-named thread, edit it into a Wiki page devoted to user-made content, and so on. How could it be appropriate for people to advertise their creations -- no matter how badly they want the rest of us to see them -- in what are essentially ad banners across the bottom of every post they make?
There is still no answer to this. Nobody has explained why they feel the need to use every post they make -- even on barely-related subjects -- to advertise their creations, or to post the same once-clever joke a thousand times until it has been run into the ground, or whatever it is they intend to use their sigs for (go ahead, tell me if it's something else! I don't know.) I think it's easy to understand that some people are bothered by the visual impact of image sigs (surely the fact that we see them as ad-banners and spamming is easy to understand, even if you disagree with it?) But nobody who supports them has provided a really good reason why they're
needed; everything you suggest is something that could be done just as easily using an alternate method... without "spamming" what you're advertising or saying into everything you post.
A sig is, in essence, a method of spamming the same thing over and over. Why do you feel it is necessary to be able to spam images in this fashion? What do you feel it accomplishes that cannot be accomplished any other way?
In any case...
Opt-in image signatures are at least less glaringly offensive; they do address most of the important logical arguments. With opt-in image sig, there is really no way for people who don't want to see them to be "forced" to see them, so the fact that no really compelling argument has been made for why image-sigs are necessary is less important (if they're really not bothering anyone, "I like them" can be enough.)
I still would rather not have them. Even if I don't see them, I can't help but feel that for the people who do see them, it will influence the way they think about the forum and, therefore, how they behave in it. Regardless of the sort of person they are (regardless, in other words, of the fact that they'd be people who would enable sigs if given the choice anyway), I can't help but feel that people's attitude towards the forum will be influenced by how it looks to them...
I feel that people are likely to be more civil and mature (whether they realize it or not) without dozens of "This poll says I am a fisherdwarf!" and "This post made by XXXGoku37XXX!" and "See my DF-themed DeviantArt page!" banners splattered around. There is an effect like this noted in the study of neighborhoods, where people are more likely to vandalize the area if they see it as already damaged or vandalized... you get the idea. Regardless of the sort of person they are normally, what they see, constantly, at the moment when they post and reply, is going to have a direct impact on how they post and behave -- if they see a cleaner, smoother, less flashy forum, they will be more inclined to make cleaner, smoother, less flashy posts.
Certainly, you can see how someone who sees a bunch of garish, spammy images every time they log into the forum could be inclined to use more garish, spammy images (or image macros, or whatever they're called) themselves? To them, that's what the forum looks like, and it'd be easy for them to forget that it doesn't look that way to everyone else -- so they'll say (on some level) "Hah, that person is acting stupid! I shall post a picture of a quizzical owl asking them if they really are that stupid, which will not be out-of-place here because, as I always see, this forum is filled with images!" Someone who is not constantly bombarded with image sigs is far less likely to post that quizzical-owl picture,
even if they would have enabled sigs when given the option.
Which leads to this...
By that "logic", if Toady offered people the option to change their forum theme to something that doesn't look gray, you'd try to VETO them too even if YOU get to see the forum in the way YOU want it. You just don't want OTHER people to see the forum in the way THEY want it.
Well, yes. If Toady posted what looked to me like an absolutely, offensively-ugly, garishly-colored forum theme and said "should this be added as an option?", I would say "hell no!"
It might get added anyway, and it's not like it's going to be the end of the world. But in either case, I do feel that the look-and-feel of a forum influences the way people behave there... and I would, therefore, prefer to post in a forum whose display did not contain options for what I feel to be garish, ugly, or spammy elements. Even if I do not actually have to see them, they
will set the tone of the forum, to an extent.