Drawing multiple sets of icons for a game

For a simple child game i need 10 (or more) sets of 2D icons. Any set should contains 50 icons and any set must be related to a single subject. For sample: animals icons, flowers icons, dogs icons, cat icons and so on. Icons must be well coloured and shaded so that they look right for children (3 to 12 years old). I need any icon in GIMP native file format (XPM), so that i can adjust them as i want. Any image must be 128x128 pixels, i will scale them as needed by the game. Icons should appears as drawed by a single hand almost in a set by set basis. Obviously they must be originals, not cut&pasted from somewhere.