Welcome to the community, @Landon_Blake!
You can send your feature requests to firstname.lastname@example.org.
The Page Designer is a pretty underpowered app. There is no direct way of adding lines in Page Designer, but you can create an empty text block (just type in a bunch of spaces for the text block) or create an empty image block, and you can add borders to those empty blocks. The borders that you create can serve as vertical or horizontal lines.
You can also add images if the images are accessible at a URL (or if the image is in your record’s attachment field), so you bring in other graphical elements as well.
For setting the page sizes, yes, you can create an 11x17 page, but for some reason the Page Designer app only understands pixels. So, you would need to convert your inches to pixels. You can use an online converter like this tool:
The Page Designer app needs much more love & attention from the Airtable team, so be sure to email them at email@example.com to let them know your thoughts & requests.