Advice just from watching your two flashes on NG
Dude, You have talent. You could do alot of good stuff. Heres what I htink you could do though.
1.) Your base animation is fine. I like the sketchy human look, its a very beautiful more 'human' way of drawing. You draw very good at complimenting faces and other atributes of humans. What you could do. Is highlight the characters a little bit more. Add a little extra textrue to the grass. and to the rain. Rain is water, water is blue, blue is not black, and water is made of droplets. draw the lines. then after that edit and color. Lil bit of depth for minimal work.
2.) Keep some of the backround rolling while your people are moving. I understand for this flash you wanted to keep it very simple. because its the meaning. but that doesnt mean that you couldent keep even the rain going on while he walked.
3.) sound effects. I watched your other flash, Pretty good. Just work on the sound quality for sound effects and music a lil. Easy idea for helping that is lower the sound of everything and make us raise voloume.
4.) your action is a lil choppy, add an extra frame or two. that simple