Is there a way to personalize a guinness glass with a picture instead of text?

Get a dremel engraving tool and do it yourself. Another option is to etch it with muriatic acid. Coat everything you don't want etched with wax. Apply acid to the bare glass and let do its thing. Each way has its drawbacks. It is easy to break a gless when engraving with a Dremel. Acid can burn your skin and destroy your clothes if it splashes. Do a web search and look on Youtube for more detailed instructions.

There shouldn't be any copyright problem if you're not creating any reproductions or derivative works of someone else's copyrighted designs. In other words, adding something to something copyrighted doesn't require anyone's permission. For instance, if make a self-adhesive decal with your gf's photo (or gf's fido) and stick it to something copyrighted, it doesn't affect the copyright. If you put a bumper sticker on a Howard Stern poster, it doesn't affect the copyright of either one....

On the other hand, if you copy the guiness logo, add something to that, and have the whole thing printed, that would be an unauthorized derivative work, and illegal.