is there any way to modify the default directory view you get on apache if there's no index.html/htm/php/shtml etc? in other words, when there's no index file, I'd like to get the directory view still- but add something to that page. like a "hosted by blah" or something, to get an extra link or two
No; because you have a directory listing. You can organize the links that show in an order by using fancy indexing in your htaccess file but that's about it.
There is a directive called HeaderName you can put in your apache.conf file that will be included at the top of any index listing. You can find more information here: http://httpd.apache.org/docs/mod/mod_autoindex.html#headername
You can use the ReadmeName directive in your .htaccess file to have something added as a footer to the standard directory listing