The image in the screenchot will not be the same as the theme i will put here.. beucase it wasn't me making the image..so I think it's correct not to pu it, and use another one...
Having a banner isn't mandatory, you could leave it off as well if you want - your choice. You could as well use the coppermine banner from the classic theme. After all, users are encouraged to change the banner, there's no need to advertize for coppermine with the banner.
Do I put the theme in a zip file as attach or put a link so people can download it?
Yes, zip your theme and then attach the zip file to your posting, using "Additional options" at the bottom left when composing your reply.
Can I put like "created by" ?
Sure, if you think you must. But then add a readme file to your theme that explains what license the theme comes with and if users are allowed to remove the "created by" link. We recommend releasing under GNU GPL.