Grid Lines

I am totally agree, it would be a very helpful tool...:)

Yes we definitely need rulers and grid lines / guides the same as in PS and AI. 

Great App! keep adding features!

Want to put in my request for this feature also...with ruler increments along two sides also!

just Wanted to provide my vote for this essential feature!

Editable grids for canvas and preview panel please.

Try PhiMatrix It runs on both Windows and Macs, and can be used with any other program, graphics related or not. There are a variety of grids to choose from, including 3rds, phi, regular, etc.

I just noticed there's no grid or rulers. I'm learning (currently on my own) digital painting with it and I love the fact I get near realistic paint physics. Painting with real paint has difficulties that can be avoided with digital painting but I don't want to lose these difficulties. It's exactly in those difficulties where the appeal of the real life medium comes from and Rebelle captures that feel perfectly. Creative people faced with limitations find ingenious ways of overcoming those limitations. Take away those limitations by making things too easy and creativity and with it ingenuity is lost. As a beginner with painting and color using Rebelle I'm thrilled that I get the best of both worlds and Rebelle has successfully balanced application of real and digital painting. I don't think Escape Motions would want rebelle to deviate from that balance as the program develops. I'm not opposed to limitations. I don't want Rebelle to be like every other digital art program. But coming from the perspective of a beginner using Rebelle to learn, I want access to resources that would aid in my journey. Resources that would be avalable in a more traditional art school enviorment. I believe a grid and ruler would qualify as that kind of resource.
I imagine an experinced artist would not need a grid and any scafolding needed would simply be drawn in. I'll be fine doing just that. I imagine the programers and others are busy with higher priority stuff.  If grids and rulers were included in some future update I think It would be a timesaver for any beginner that would like to focus on other aspects.
A friendly thought shared by a very happy customer.

While maybe not so variable like Artrage Stencils
but I think Rebelle Stencils could be also used
as a workaround for this.

Rebelle Stencils are simply grayscale images
so they can have any content