Dear Samir,
0.1uF bypass capacitor between VPF --> VPP & VNF --> VNN is ok if operating the LM96551 with MODE = LO.
But, it is recommended to add an additional 10uF between the pins if operating the LM96551 with MODE = HI.
I would suggest using the combination of 0.1uF+10uF or 0.1uF+1uF+10uF between the pins to provide urself more flexibility. Make sure the voltage rating for the capacitors is around 100V as well.
I think Charles was also suggesting the same in the link:
http://e2e.ti.com/support/other_analog/imaging_afes/f/239/t/226250.aspx
I hope that helps.
Thanks,
Rohit