The best snacks are those with protein and veggies (like the celery and PB/LC cheese option) because the veggies fill you up and the protein keeps you full longer. Both keep your blood sugar stable too.
In Phase 1, if you are feeling the effects of detoxing (feeling sick, dizzy, tired, cranky, etc.), you really will benefit from incorporating the good carbs that are allowed during that phase, like bell peppers, beans and legumes (chickpeas!), and tomatoes. Try cherry tomatoes stuffed with Laughing cow cheese, or bell pepper strips dunked in hummus (made with chickpeas). My ultimate favorite Phase 1 snack is a serving of homemade (store bought has immense amounts of sugar!!!) three bean salad. There are tons of recipes out there, but I like to make mine with splenda in place of sugar, green beans and wax beans (to up the veggie quantity) and at least kidney beans and chickpeas. If you whip up a batch at the beginning of the week it lasts for a long time and gives you lots of quick snacks. The fat in it helps keep you full longer as well, and the fiber in the beans helps keep you 'regular', something that can also be a problem during P1.
Variety, IMHO, is the key to success on any plan...don't let yourself get into a rut...do what you did here,
Sail, and post so we can all help!
Good going!