For the Profile picture and also the attachments page, there's no message on the limit to be upload. Sometimes, when the users do not know about the limit, they upload the file and will receive a message like the following one:

This is a feature request have a Warning with the size to be uploaded in the instance. For example, for the profile picture, the attachment size would be of 1.5MB. And for the attachments itself, we could have the limit message near to the upload option, near on the following example: