Sonic Riders Style Goku!

[Vipershark]

Are you using mspaint?

To resize things, don't use the selection/drag box.

Instead, select what you want to resize using the selection tool, then go to Image > Stretch/Skew.
Then set the Vertical and Horizontal percentage boxes to how big you want the sprite to be resized.
(For example, setting both to 200 makes your sprite twice as big, 300 three times, 400 four times, etc.)
(To make something smaller again, go down in increments of 25, 50, or 75 percent.)

As far as colors, you need contrast. Better advice would be to use the colors from goku himself to color the board.
And stop working on a white background. Use a nice, non-eye burning color such as a dark blue or dark green that contrasts well with your sprite.