Yeah, I got sick of that tileset eventually. One time I tried to make a second set to go with it, but eventually ended up re-inventing it altogether.
Then I reinvented my reinvention when I came to use it in one of my levels. If you're interested, I've attached it below, with some examples of use. It's not brilliant, I admit, and it's a bit of a pain to use, but you could consider it if the corners bother you.
The screens look pretty good for a first level, though your difficulty might be higher than 'normal'. The third of your screenshots looks harder than normal. It's a hard thing to judge on your first go.