I am a big fan of using something other than the numbers on the scale as mini goals. The numbers vary so much, and don't always tell the truth about your progress.
Some things you might want to make your mini goals:
losing sizes of clothing
moving along in exercise routines (increase time or distance for example)
Sticking with your plan 100% for X number of days
Cutting a bad habit out entirely (eating fast food, eating sugary treats, etc)
Some scale based goals can be:
10% of weight lost (so, 110 lbs = every 11 pounds lost)
Meaningful numbers to you (I had a mini goal that was my husband's weight)
25% are good goals as you mentioned.
I never really rewarded myself since meeting the goal was reward in and of itself
I guess right now.. I am wearing loose 14s in most of my clothes, but I am not buying new until I can get into 10s. So when I reach size 10 I am rewarding myself with clothes - that's a fun reward if you look at it that way. Reality is: I am just cheap haha!