change image channel?

[xony]

when I publish a channel and do I change him/her the image, doesn't he/she give me any error, but doesn't it change the image for that it can be? does he/she have to have the same size or something like that? thank you.

[admin]

Check permission of chimg folder and images inside the folder, this should be writable by by web server user, on most servers, chmod 777 will do that.