Nice CR, well done mate, looks like you had a great time! I will try to assit you with the picture problems, if I may. If you click on the pic, you will be given the file path (Where is it located). I understand from the path that the pictures was loaded in Photobucket album under caranx50 title. The uploaded size is at 800 pixels height, varies on the width, that's okay.
If you click on the picture property, will find the file size significantly smaller on the pictures that are pixilatted as compared to your better ones. What I think happened is that the pixelatted ones were over compressed hence, effecting the final image. If you have edited or corrected the pictures, you will be asked to save in Maximum, High, Med and Low. The image quality saved was too low, therefore the file size was smaller and pixellation occured, so to speak.
All is not lost, you just to start from the original pictures in your memory card again. Perhaps saved in a higher resolution. Try to shoot always in the highest resolution the camera can handle, there are 2 areas you need to take note of; Image Quality and Image Size. You can select highest quality with a preferred image size for your needs. BTW, the pictures that are pixellated came from a different camera and they were all from that same camera, check your camera settings, perhaps. Cheers, you have a good one , mate!