yes, the "basic" grip looks correct...however, if you do a search in this forum, there will be a modified grip if you happen to play a shuttle that has gone past you-->it's gonna be more like you forehand grip... For now, just keep practing with the grip..or get a coach to help you.. To strengthen your wrist/hand/fingers and backhand off the court, you can do weight resistance using heavier object(ie. tennis or squash racquets or a long-neck bottle filled with some weight)...work your way by doing repetitions to mimic the actual backhand motion to strengthen your wrist, until you can't do(your wrist area feels sore) the reps with those heavy objects..Use your fingers also to do those repetitions..Do them slowly and little by little at first, then work your way up in terms of reps..With consistent practice and training, you'll most likely improve your backhand, say in 6-9 months...or even less.. Good luck-
From the photo, it appears that your thumb is placed on the large part of the handle. This is the right grip for many backhands in front of your body. But you are probably revealing too much of your palm. You may need to close the palm more so that the hand can keep hold of the racket and stop it wobbling about. It's a complicated issue, because the grip tightness varies a lot depending on the stroke, and during a stroke the grip tightness will also change a lot. So all I would suggest is this: keep your grip relaxed, but make sure it is firm enough so that you can control your hitting action.