You can easily convert them to pdf files by using a virtual printer and Printing to create the PDF.
You can create jpg files but it is difficult to create multi-page (multi-jpgs) to split a larger design into smaller sections. To do that, you EXPORT the pattern to an image. For a multi-page effort, you must specify what sections to put in each jpg and do the instructions separate. It looks like a lot of effort for anything but a very small design. You also do not get the bolder line every 10 stitches.
If your customers use Windows you can instruct them to get "Power Toys" for Windows. Once it is installed it will let you see .PDFs in thumbnail mode without having to open them. If your patterns are relatively small and can fit onto a single .PDF page then your customers should be able to see the entire pattern in thumbnail mode. I'm not sure if this works for previewing .PDFs from a website.
PowerToys will also let you see all of your .SVGs, .FCMs & project files (Brother Scan N Cut files) in thumbnail mode as well. Super useful if you've got a digital cutter from Brother, Cameo, Cricut, etc. I'm not sure if this is a feature of PowerToys or PC Stitch 11 but I can now see .PAT files in thumbnail mode. It just opens up the potential of your Windows PC to something way more useful. You can learn more about MS PowerToys here: