Hello,
It's good to have you in the jam, and GREAT that the sweet Raspberry Pi (400) tempted you in - as was surely the intention :-)
I agree that Adventuron is not entirely friction free - there are many rough edges, and for pure text games, it's a lot less powerful due to its database-centric design. The editor too has its quirks.
If you can express your issues then that would be wonderful, in order to help with future development and future priorities. A lot of the existing problems are known, but it still helps to prioritise if I can hear what specifically troubles you the most.
The graphic design part is tricky, and it's good that you have time to work on it. Don't forget also to choose an appropriate font, see the documentation for a table of fonts designed by Damien Guard, and how to add them to your game, or choose any ttf font you like for your game.
Anyway, great to have you on board, and good-luck !
Chris