User-defined avatars - we don't want to have to store avatars, or vet them, or get angry if someone changes avatar to something abusive.
If it's something less gross, say annoyingly repeating attempts at trying to get the same disallowed image approved, you can implement the same sanction but maybe minus the enforced dunce cap and with a lower voting sample and easier ratio required to get it back.
I reckon there's enough people posting and voting for an idea like that to work, and I know I honestly couldn't care less about waiting a week to a month or more to see a batch of icons get approved. I know it's going to take someone a while to sift through the requests at first, and I don't think people will make that many requests when they realise it takes a week to a month or more for changes and updates to be approved.
If there's a hardware issue, you could always go the whole hog and make it a feature of a Register Plus Ad Free Paid Membership or something. Keep Free pretty much as it is (maybe fix the threading issues, oh please fix the threading issues), £10/year per member to hire a few terabytes in a rack somewhere, buy your own fat pipe and some boxes, or some kind of big blob of virtual cloudiness?
How much do you reckon you make per commentard (as opposed to, ahem, read-only viewers) from the ads at the minute? If the price is right, I reckon there's people here who'll buy into extra bells and whistles and a full page of news minus the ads, even if you can just run ABP+ for the latter feature.