When adding an image, sometimes I'll drag in the wrong screenshot or realize I have a better one to add. Would be nice to be able to edit and delete images just like you can with text comments. Know of any way to do that? Or if they're planning on adding that ability in the future?
You can't edit images, but opening a card will display a list of attachments (images, spreadsheets, whatever), each one should have a Delete link next to the right (just below the file size).
Click Delete, click the big red Delete button that pops-up and it's gone.
Well, there is this tool I wrote, Trello Attachment Editor, which lets you edit and replace attachments inside of cards without having to manually download and upload them.
The process is simple, but currently it only support text files.