If you believe a post violates the rules or is low quality, you may flag it for review. This sends it to the moderation queue, where it has three days to be re-approved before it is deleted. See howto:flag to learn more.
You must give a valid reason for flagging a post. Explain concisely why a post should be deleted. The following are some common reasons to flag a post:
Off-topic: Not anime-related, such as photos of American porn actresses.
If this post was automatically deleted, then it means that the janitors that reviewed it thought it didn't belong on this site. If you still believe this image was wrongfully deleted, then you can appeal its deletion.
All users are limited to one appeal a day. For more details, please read the wiki.
This feature will allow you to replace a post's image with another image in place. If you are replacing something other than a sample → full-size image, you must be careful. See topic #14063 for further discussion.
Identical image with missing or corrupted metadata → image with correct metadata (post #2196287).
Identical image with worse lossless compression → image with better compression (post #2766377).
Sample with already uploaded full-size → inferior identical image from alternate source. This serves as a way to grace posts (post #2753690).
Images uploaded on accident by a user (corrupted images, incorrect tweets, pre-revisions, etc.). If done in a timely enough manner, this should also be appropriate to use for that purpose. Fixing the order is also permitted to some extent.
What is typically discouraged:
Identical images from different sources (unless you can confirm that an artist uploaded a sample to one site and not another). See topic #14595.
Images of non-identical filetypes that aren't samples.
GIF/MP4 file → Ugoira. Ugoiras are not considered necessarily better than their GIF/MP4 counterparts (post #2625276). Upload it separately.