Chiptune labels aren't record labels really.
I think the only reason to release on a label is that /some/ of them apply a certain level of quality control on what they release, so your music doesn't get lost in a sea of shitty releases. That's not true of all labels however. Your music stands a marginally better chance of being discovered by random people if it's on a label that's well known, but that's not exactly verifiable data.
Otherwise, I think the "promotion" part is utter bullshit. 99% of labels will make a facebook post, a CMO post, a twitter post, and maybe a small youtube video for your release. Beyond that, nothing that exciting. All of these things, you can do by yourself in a matter of minutes. You can make your own print-on-demand CDs on Kunaki. You can manage your own Bandcamp page. You can spam your releases on every freaking chiptune facebook groups, etc etc.
In a way, chiptune labels have adapted to what chiptune artists are: hobbyists. They don't "sign" you up on a proper release contract, with schedules and budgets and whatnot. They "hire" any old chap who calls himself a "mastering engineer" and pay him 20$ to put your song through one of Ozone's preset. It's a very mom and pop affaire, because there's no need for anything more serious because 99% of the scene is composed of people who are doing it for fun. Nobody makes a decent living out of chiptune albums, and that's not going to change anytime soon.
So... to answer the original quesiton: any label will accept submissions even when they say they don't. If your demo is short enough and easy to access online, they're always going to at least scroll through the songs quickly. If your stuff is stellar, you'll get a positive answer. Just remember that your shit needs to stand out from the rest. Stay humble when you get rejected.
My advice however, is to DIY the shit out of it and release on your own. Make your presence known. Collaborate with people. Be part of the scene. Spam the groups. Be active. That's way more promotion than you'll ever get from any netlabel.
Yeah, good points. I've given up on sending my minimal stuff to chip labels, and may even give up on sending it to non-chip labels.. it just doesn't seem marketable in its current state. I'll just keep releasing it quietly on bandcamp for now; that way I can make it as repetitive and long-form as I want, without someone at a label telling me I need to edit my tracks.
It seems fitting with the aesthetic to have a minimalist release format as well. Uploaded to bandcamp, posted on facebook, maybe posted here but that's about it.
Anyway, my youtube videos have had more plays than my albums.. maybe that's the way forward for this stuff..?
On the other hand, I've been in contact with Perelandra for my main Pselodux project, and while they're small, they're very responsive and provide just the right amount of feedback I need. I'm currently working on a super complex prog album for them, hopefully done by the end of the year 
not to another gba . We just gotta wait for that prime mono cart . Then cross sync with some 2.7.9 and we got a deadly arsenal of sync !