An animal footprint

Some rain water may be left in the footprint. Pump it out with a piece of sponge and clear the sides of remaining leaves and stones.
To finish this process you will find some info here

A vegetable imprint

Cast some plaster into a small container (flat and wide)
Once the plaster is almost dry delicately set a leaf (oiled) on top or put in an oiled acorn.
The plaster will reproduce the nervures of the leaf or the nice shape of the acorn.

Leaf drizzling

You may have gathered nice leaves.
Let them dry for about a week in a directory with a heavy dictionnary on top or use the herbarium that you have made for that purpose.
Put the leaves on a blank or coloured drawing paper
Spray some paint (not too liquid) using an old toothbrush and your thumb so as to make a nice "drizzle" of paint over the paper.
Once dry, delicately take the leaves out. Their nice shape will be marked on the paper.
This technique is great if you want to decorate a display cabinet in which you can put your discoveries.

Mushroom imprints

Put somme button mushrooms on a blank page (take the tail out)
Leave them for at least one night.
Take the mushroom out. The spores (meaning the seed of the mushroom) have left a nice brownish pattern on the page.

You can use it as a decoration for the menus or the invitation to the yearly gathering of your unit !