Gina, maybe, some of the regularly spaced, small tiles, were purchased that way & "cut", for the design shape, of the stained glass & may have a "backing" to them, for larger surfaces & cover areas, for improvement/ replacement, of old tiles. Maybe a big box store carries that, type..
While some particular colors of stained glass, are much more costly, due to certain ingredients, used to create a specific color... There is some glass, that were designed for use in space shuttles & that is some awesome glass ! Not sure if you can find any of that. I was realizing, that not much "beach glass" can be found, much, any more. But, there's even an NGA member here, that sells it on Ebay,, yet that would be Mediterranean beach glass ! I'm just trying to think of what might make yours, outstanding. I know there's an art glass museum, over near Clearwater, Florida... Up here, they do blown glass classes & I'm uncertain if you can get any remnants, of a "studio" that does near you.. Just a few ideas, that 's all.(To consider..) I'm sure you could get plenty of images & ideas from Pinterest, & Google "images", to get certain ideas for plans.. Maybe a magazine (online) has an article about these kinds of projects & gives resource names, with address, too... Have fun with it !

Gina,
If you are looking for colored glass I have access to a lot
I live near Kokomo Opalescent glass, it was used by Tiffany in his colorful creations.
They sell scrap buy the pound and I have a box or so from long ago projects.
Be glad to send some your way for postage .
Just let me know

Cinda

That must be fun to be near that place, Cinda! Glass is so beautiful!

I looked at the board substrate today at Lowes while I was geeing some algae cleaner for the walls. Its BIG can it be cut and how?? Will it still be waterproof on the edges if its cut?

If you are into using a kit, there's a lot of them available
For example:


https://www.etsy.com/listing/6...

Cute

My husband cuts the substrates for me. I think a few can be cut with a circular saw, but some of them he just scores with a box cutter and then snaps the line and it breaks perfectly. You could ask where you buy it to know how to cut it.

Or maybe if I act helpless enough they will do it for me

Many times the builders supply stores will cut for you if you know the measurements you want. Many folks don't have a large enough vehicle to carry large sheets like that.

I hope to follow and see how your ambitious efforts turn out!

You're right. They will usually cut them to size for you. I'd forgotten that.

Oh yes, we definitely want to see it when it's done

Oh no pressures on LOL!

Gina, that made me think back to Rainbow Tower, on Waikiki Beach, as I used to reside at the Ili' Kai Hotel, on the waterfront ( 2 bedrooms, each with full baths on each end , with kitchen & living area, between, plus several lanai.)
It may be part of Hilton Hawaiian Village. Now, if they can do that on a building of that size & grand scale, I'm fairly sure, you can manage a project, like you are getting ready for. I just have no idea, how they did that one. Have you ever seen it ? If not, have a look at the some of images of it , with Diamond Head, nearby !

It was completed not too much before, we'd moved there & I think it's over 260 feet all, nearly 70' wide & may have used over 15,00 mosaic tiles ! Better get busy, learning how to "score' (& not just obtain some tiles. too.. I know, they make great tiles in Mexico 7&maybe there's a vendor in Southern California. Up in PA. there was Moravian Pottery Works, too. I used to take a diamond tipped blade, for scoring "cutting" stained glass & it may take a little practice. Use safety wear & flat nosed pliers... ( I even did used wine bottles, to re-use & make drinking glasses !) Once you've come up with a design, to scale, then go from there.
I've seen swimming pools, that were done, with tiles installed at the bottom, just so you could see & enjoy the work, & admire it from above...Maybe you can coordinate with a theme, of some gardening aspect, you particularly enjoy.

Well I did start cleaning the wall today. Its going to have to have more cleaning and be painted before anything can be put on it!