The ones in the pics seem ok and all ... but if you really wanted to get the full benefit of doing those two neck exercises in the picture, it might be a lil' better to have someone else putting the resistance on you with either a towel across your head or a weight ... (since, in practicality, your limited by your own strength, esp. in that awkward position, if you are doing them by yourself) ....
I think, overall, you are going to get more of a good base for neck strength with neck bridges, including front neck bridges (on your forehead), side neck bridges (tilting to the side either from your forehead or back of head), and back neck bridges (on the back of your head). The great thing about these, is you can always have your two hands placed right above the ground in case you can't go on or if something happens so you can stop whenever necessary.
On these neck bridges, try to keep working to get your body as parallel to the ground as you can on each different neck bridge (rather than having your butt or pelvis wayyyy up in the air), even to the point of where your nose is touching the floor just barely (like on those front neck bridges).
Word of caution: Seriously, be very careful with neck bridges. Don't make any sudden movements when doing these: ease into position, esp. if your not on a mat and your on a hard surface like carpet. Be VERY careful on side neck bridges, as the muscles stabilizing your neck to the sides usually will not be as strong as those in the front and back. Also, just listen to your body. If you are getting weird cramps, sharp or dull pains while doing them or something, stop! (not talking about having sore neck muscles, but actual pain in the vertabrae/joint and what not). Wait a couple of days and see how your neck is doing ... time will tell. Like an idiot, the first week I over-did them and didn't listen to my body and had a bad neck cramp for the next 2 and half weeks ... and I consider myself fortunate.
Hope all goes well. Let us know how it goes. You'll have Matt Hughes neck syndrome in no time.
btw You might want to ask this in the grappling forum as well, as many of those dudes know a lot about neck bridging and stuff ...