You are on the right track.
Always change the .jpg name of your image to correspond with what it is.
Then use the alt tag to describe the image with the same words i.e.
joe smith.jpg alt tag: "this is an image of joe smith".
Lastly write a description using the same keywords beside/underneath/around the image in your website/blog.
Now Google Image Search for some reason takes a lot longer to index images than Google Web Search takes to index websites/blogs.
I would say at least 3 months and sometimes longer. That's just the way it is unless you have a real high
PR site.
My image gallery website took about 2 months to start indexing images after the site was indexed in web search.
Just do all of the right things and be patient.
You could also get a Google account, go into webmaster tools and add your website then opt into 'enhanced image search'.