First, the length of time to get featured mostly depends on the stream and the stream settings.
This one was stuck for almost four months in the approval queue
of a user created stream set with "No automatic approval" and a single moderator that deleted their account.
imgflip.com/i/3iu8zh
The site has recently made some changes for abandoned user created streams, so that they are easier for other Moderators to claim and take over running them.
For streams owned/promoted by the site, like the fun stream or the politics stream, it can be up to 12 or so hours for Submissions that aren't auto-approved (ie, on an established meme template, no vulgarity, content that appears to be safe-for-work) I don't have the stats at my fingertips, but I'm guessing maybe less than 0.1% of submissions take more than 12 hours. It's been up to 12 hours for review the whole time I've been here, even before I became a Moderator, it's usually shorter though.
If submissions sit in a stream that I'm a Moderator of for more 12 hours, I get a notification, I'm more likely to get those reviewed first if I'm around.
There are only three Moderators on some streams owned by Imgflip. I'm guessing that could change if the usual 12 hour max turnaround time gets out of whack or the site owner wants to open those streams up to wider moderation.
Only takes one Mod to feature a submission.
