I'm designing a News Feed system using PHP/MySQL similar to facebook's.

I have asked a similar question before but now I've changed the design and I'm looking for feedback.

Example Notifications:

User_A commented on User_B's new album.

  "Hey man nice picture!"

User_B added a new Photo to [his/her] profile.

     [show photo thumbnail]

Initially, I implemented this using excessive columns for Obj1:Type1 | Obj2:Type2 | etc..

Now the design is set up using a couple special keywords, and actor/receiver relationships. My database is designed for efficiency - using a table of messages joined on a table containing userid,actionid,receiverid,receiverObjectTypeID,

Here's a condensed version of what it will look like once joined:

News_ID | User_ID |                  Message                   |     Timestamp

  2643       A       %a commented on %o's new %r.                  SomeTimestamp
  2644       B     %a added a new %r to [his/her] profile.         SomeTimestamp

%a = the User_ID of the person doing the action

%r = the receiving object

%o = the owner of the receiving object (for example the owner of the album) (NULL if %r is a user)

Questions:

1. Is this a smart (efficient/scalable) way to move forward?

2. How can I show messages like: "User_B added 4 new photos to his profile."?