I believe I've mentioned before on here how I struggle to come up with forms for letters.
I've tried to solve this by looking at other systems. Despite the diversity in our world, I've found it surprisingly hard to find a multitude of systems to draw from.
The problem is: writing systems have different factors that can influence their design. Syllabraries tend to have more complex characters than alphabets, because they don't have to write as many of them to spell out a word. And besides, they need a wider diversity of symbols anyway. Logographic systems are no different. Also the medium makes a huge difference. The aesthetic of one script may not be too practical to replicate using a medium it wasn't intended for.
I've found this all divides up writing systems into multiple different categories based on design. This means that if you stick with a certain medium and type of writing system, you won't have much to go off of. Like, if you look at alphabets, all that really seems to be out there is Latin, Greek, Cyrillic, and Korean. And if you look at cursive scripts, you only really have two options: English cursive, and Arabic, which is technically an abjad. And of course if you want a logographic system, the only living logographic system (aka, the only one to see use in a world where literacy was normal writing was part of every day life) is Chinese. Beyond that, all you have to look at are long extinct logographic systems that were all made to be carved into stone. Or cuneiform, which used some rather odd tools and medium to write. How many systems do you know of that were written in clay, and were always stamped rather than drawn?
I can't come up with forms that really look overly different from the few alphabets currently in use. Worse yet, most of them are closely related to each other! It seems like every symbol possible has already been used in a writing system somewhere.
The only thing that has really helped me is I've noticed that most lower-case Latin letters are built from a limited number of shapes: a circle, loop, short line, long line, long line with a loop, and a dot. Sadly, I can't really come up with any practical letter forms that don't use these shapes. They're pretty simple and basic.