I took a look at those two. I noticed those images are used on alot of websites. It might be a copyright issue where people are paying to use an image or own the image and are not sharing it for fair use, but that's all just a guess. I've read there are ways to check online if an image it's copywrited, but have never done that.
I've had problems with memes not featuring occasionally, last time was pretty bad and I heard more than one user mention it. I think that round of problems (in April I think) was maybe from a website upgrade that had some bugs, but it's purely a guess.
I checked my submissions for the past month or so and I did have one that never made it about 3-4 weeks ago. That one has an image clipped from an album cover and at the time I thought it didn't feature because its a partial copywrited image.