I love to make (and eat) sushi!! I stick with vegetarian also. Your rolls look great - esp. for a first try!!
Do you have a sushi mat for rolling? I wouldn't even try rolling sushi without one. It allows you to make nice tight rolls. I took a sushi making class years ago and here are the veggies that were suggested in that class:
Kampyoo (dried gourd) which is washed with salt water and boiled in dashi, soy sauce, salt, sugar & mirin. If you want the exact directions let me know, but I just found out recently that you can by the kampyoo already cooked in the seasoning in cans - a LOT easier. (You'll need to have an Asian market nearby to find it though.)
Spinach - steamed or boiled till wilted
Eggs - beat 2 eggs with 2 t sugar and a pinch of salt. Make a thick omelet and cut in 1/2" strips when cool.
Carrots - cut in 1/4" sticks and cooked till crisp tender.
You can combine all of those ingredients for a "Futomaki" roll.
Other possibilities (for more Western pallets):
Cream cheese and smoked salmon (this was a HUGE hit at a party recently)
Add avocado to the above (or just about anything with cream cheese)
Cucumbers
String beans (cooked till crisp tender)
Crab or shrimp (cooked)
Also, just wondering if you added the rice vinegar/sugar/salt mixture to the sushi rice and tossed it into the rice as it was cooling? It does make the rice taste more "authentic" than just using pain boiled rice.
OK, now my mouth is watering!!
Jeanie