Get an app like kphotoalbum or gphpot2 or picassa. Trying to rename all the hundreds or even thousands of pictures is a lost cause. First off it takes a lot of work, then you have to worry about compatibility, then worry about crappy photo viewers that display by name instead of the date, etc.
There are proper fields that you can add descriptions and such, do a search for EXIF data and read up a little bit. Most OS's can display those fields and most programs can display and edit those. That way you leave the original file name short and unique to keep compatibility and can add whole paragraphs in the description, comment, user comment, etc fields where your not limited to certain characters. So you use your photo app and select a dozen pictures and then label them "summer vacation to paris" or something descriptive in one of those fields which can be duplicated. trust me, after trying for the first few years to rename and think of uniqie names then have to go back and try to rename again to keep order and such its not worth the trouble.