As far as I know if you don't like one or the order, you have to delete all and start over, can't just replace one or change the order. (At least if you are still in the old dash.)
Plus new images can take up to 6 weeks to show up. So you want to take your best shot and try to get it right the 1st time if possible. Image uploads are just kinda funky. Hopefully some of those issues will get better once we all have the new dash.