Note how the name actually overlies the strip. This is so people doing screen grabs can't capture the image without taking the caption with it. It's a little intrusive, but for frequently copied webcomics like C&H, it may be seen as a necessity.
If the goal is not to attach the strip information to the image, then a simple magazine-style caption, such as Above: A Webcomic, might suffice.
Be wary of text located near an unlabeled image. A search engine might lift some, thinking it goes with the graphic.
3. Using ALT attributes
ALT attributes are the part of a link that is used to identify images. This is the most professional way to manage. They are called attributes because they are an attribute, or a portion, of a link.
It's also the way of the future. Automated readers for the blind rely on such tags to explain images.
Explaining the execution of an ALT attribute is beyond the scope of this article, and it is explained elsewhere with clarity and detail. But for those unfamiliar, and depending on your platform, ALT attributes are simply inserted into code and associated with a particular image.
You may already be familiar with making an image into a link, so that clicking the image takes you to a new destination. ALT attributes are an optional component of that link: they appear if an image fails to loads, informing what's missing, and they tell search engines what an image is about.
Inserting tags and attributes goes easily on Synthasite, the system I use. You simply indicate what item you are tagging, and drop the tag or attribute information into a designated box. This makes tag updating extremely easy.
4. Tell the searchers everything
Every image on your site, except for advertisements, should have an ALT description. I don't know, but suspect, that search engines respect you a bit less if such tags are missing.