I can share some tips and references that should help you on the way. To change the default shape, you need to play with pane, yAxis.plotBands and pane.background settings (you can create a custom shape for the background). As for the range, you can easily set it with yAxis min and max options. As for the labels, you have yAxis.labels settings, and there are several ways to set your ticks, just check yAxis.tick options.

Please see the demo attached to this API option to take a look at the way to extend graphic options with SVGrenderer: https://api.highcharts.com/highcharts/series.scatter.marker.symbol

I hope that these would be helpful, happy charting!