on :
FileStream fs = new FileStream(savepath + clientname + "_" + lblimgname.Text + ".jpg", FileMode.Open, FileAccess.Read);
change it to :
FileStream fs = new FileStream(savepath + clientname + "_" + lblimgname.Text + ".jpg", FileMode.Open, FileAccess.ReadWrite);
then after img.Dispose(); set your picRightthumb1.Image = null , then delete it ....
try then tell ..