Replacing All Tiles Of One Type

You can use masks to easily replace all tiles of one type in your world.
    Use the brush tool
    Unlock the ratio
    Set Height to maximum
    Set Width to minimum
    Zoom out
    Swipe the brush across the map a few times and all tiles of the mask type will be replaced with the brush type.
You may want to only swipe over some of the map at a time if you find the editor starts to slow down or crashes.

Using Schematics To Build

You can use a schematic pack to load in many pieces of furniture facing different ways. You can then paste them from the Clipboard to quickly build rooms and bases how you want them.
Other uses include artwork that can be re-pasted as seen fit to give an area a certain theme. A popular thread on the Terraria forums for schematics: schematics
Check out the Clipboard page for precise information on how to load and paste schematics.

Using Chests

Chests can be used to control progress in adventure maps. You can put down chests along a player's journey with better gear in as a reward for passing a trap/puzzle/maze. To edit a chest right-click on it while the [[Toolbar#arrow-tool-a]] is selected.
If the map requires that the pickaxe (and/or other tools) are thrown away you could use chests at puzzles with limited amount of blocks stored inside, requiring that the player must figure out how to use the blocks to beat the puzzle. Sand can be particularly useful in this case because of how it is affected by gravity. However, since the player would effectively only have one shot at trying to beat the puzzle it would probably be best if this puzzle was not required to be beaten to carry on with the adventure but would give a good reward if the succeeded in doing so.
In the 1.0.6 Terraria patch there are now locked chests! One way to use these in particular is to limit the selection of gear players start out with (or carry on with at certain "checkpoints"). You can do this by putting a golden key(s) in an unlocked chest. Then you can put gear setups in locked golden chests, forcing the player to choose which chest(s) to open. Make sure you signpost what each chest is for though, unless they are meant to be a mystery!