To know how many images are indexed by google images (filter by keyword) :

you can type the following command in google images : keyword site:yourdomain.

None for me for now 

Thanks Leo 

I found the same as Franky, I had a few days where I did not upload and it seems that all up to about a week ago have been indexed

But it is on that page - it is thumbnail, found in similars below your image.

actually, you can skip the keyword

site:domain.com shows all your images

what's strange is that I get many more indexes reported this way than with google webmaster tools

for both my sym site - cascoly-images.com and my travel & education site - cascoly.com I get about 40 images in tools listed as indexed, but several hundred thru google images!

what's really encouraging is how fast the sym site is getting noticed -- my much older smugmug site still only has a couple dozen images indexed - might be a google search related downgrading of smugmug

once again, thanks Leo!

that's right, Google is right there after I publish an image, just like a dog;)

Perhaps can be useful, but at least this is a process that everyone must doing by himself. I say this because I think that all us, must choose where and how to place the write. In my blog every photos has the write, in future I'll change it, (less distracting), but for example I never put it in the bottom where can be cut easily. So at the end the risk for you is to have more request to refine the process to fit the need of all. To do this we need a plug in for watermark or put the write before loading the photos on the site via photoshop gimp aperture etc.
To me is important the write "www.xxx.c" the metadata are stripped easily, I pay attention with the images, and more time pass, more is the attention.
In last days The UK parliament approved the new Bill about the copyright and is a panic law http://www.microstockgroup.com/general-stock-discussion/copyright-in-gb/
So if this is a simple thing to do OK, but otherwise don't spend much time in this.
My two cent.

to print the website www.whatever.com (c) at the bottom center of each image?

+1, I have my site name below the logo yet it disappears on wider images. Although I don't consider it as a most important feature.
Check this out, I just found few plugins while searching for [watermark fly], I'll try it tomorrow. Maybe it could save you some time

Well.. I found a few, eliminated to one  [Simple Image Watermark], but it doesn't work, as we want because "watermark will be applied automatically when you upload images to posts", as most of those.

I think it ill be easier to make it as a feature, instead of wasting the time for a search;)