Heh its a neat catchy riff but im stuck with it ... cant ad something neither to the beginning neither to the end ... plz someone have any ideas ?
Well, here's a few suggestions. Write a lick to follow it that's unexpected. Or write a lick or riff that's in a different key and has a slightly different feel. (Like this one's happy, write one that's kinda tense.) Or even make a different rhythm for this riff to play on like the third repitetion and then go back to the original rhythm.
Try a different chord progression. I.E. Instead of I-IV-V, use II-V-IV or even I-VI-III or something.

Or you could let the guitar drop out and have the bass doing something for a verse or something.

Or you could throw some different instrumentation in there... Add a sax/trumpet melody or something like that.

Just a few ideas. =)