Other similar items that can be placed in water (but don't last as long as driftwood) are dead oak leaves,dead almond leaves,dead true palm (not cycad), leaves,pine cones after boiling,Hickory bark(in tanks where fish won't destroy it).
Eucalyptus leaves are interesting ,however you need to get rid of the oils first,do this by placing them in a bucket of water outside,replace water every couple of days,do this until water no longer appears oily
How to decorate with driftwood: decorate to your aesthetic interest,just make sure wood is placed so it wont injure inhabitants.
Wood can simply be placed on the bottom or leaned snugly against objects, or you can use fishing line to turn it into a island or suspend it in the water column.
You can have part of the driftwood breach the waters surface,this above water portion can have mosses,bromeliads,airplants and other epiphytes attached to it,or even certain fungi. This could also be used as a basking/haulout area for semiaquatic animals.
Driftwood can have certain aquatic plants such as Phoenix moss,flame moss,java fern attached to it in freshwater,or sponges and sessile worms attached to it in saltwater