your quilt looks great. I would be sure that you follow directions on the batting package before I decide on how to quilt it. Some batting you quilt 10" apart and some you have to quilt 2" apart
I would suggest quilting next to the seams as well. that seems like a good start and you will have the seam to guide you. If you get the quilting done with stitching next to the seams - the I like osewme's idea of the echo quilting.
can you make a practice sandwich to practice quilting on before you start on the quilt? That might help you gain some confidence