You are doing a very fine "job" of coming up with new challenges. Thanks for doing that. :-)
Here are some comments (things I have learned from experience):
1. About walking challenges... there are step and mile challenges that are already on the team each month... in the Exercise Forum rather than the Challenge forum.
2. Also, about walking. There are quite a few people on the team who can not walk for one reason or another so it's best to have some challenges to Exercise....rather than using the word "Walk".
3. Most people prefer a challenge that is a day to a week long with several options...like one food option, one exercise option, one Goodie option, one to "avoid" a certain food, etc. That way they can pick and chose what they want to do for the challenge.
4. Try to start a weekly (or 4 day or 5 day etc) challenge one time a week to keep people coming back for more. :-) That also helps the MANY new people who join each week. If you only have very long challenges such as walking across a certain distance.... what are the new people going to do? Also, as Tammy says, people really love the ODC, One Day Challenges.
Keep up the good work and a big HUG to you!