handling Elevation

I'm planning on creating a few maps for my 4e D&D group and would like to feature elevation. I've got two specific ideas in mind which include a fight through the tree tops, across large branches and a fight in a forge with various walk-ways at different heights. I've got ideas of players needing to deal with archers shooting arrows down at them and various other elevation related obsicales. However, I'm struggling to figure out a good way of handling elevation and representing height on the 2D maps. Does anyone have any tips?

I use two different methods. The first is just adding the height to the name. The second (for shorter heights) is using the numbers on the status icon that looks like a pair of angel wings. I use a multiple of 5. Example: for 25 feet off of the ground I use a "5".

I'd add a 3rd method personally, multiple maps, each representing a different elevation. For example, for the tree example, you could have: Map with the ground level. Map with the lower branches level. Map with the middle branches level. Map with the upper branches level. Then as PCs go up and down, you move them across the maps. Before the last rugged reroll you had to do this on the same page so it was best for smaller maps but now you can split the players across pages, so you can do that for big maps as well. I'd usually use this if moving between elevation takes at least round of combat, or a special action (slide down a rope, climb a ladder, etc). You can then combine Gauss's method within a map for small scale elevation variance, and this one, if the battlefield is vast.

If a creature's name is Orc, change it to Orc +5 if the creature is 5 squares (or 25 feet if you're using feet, etc.) above the ground. Just make sure everyone can see the token names.

I heard of some people using tiles with differing textures to represent higher/lower elevations. They mark them with the elevation numbers like +/-5.

You could also use the map layer for one elevation and token for another. You have to play with front and back a bit but you get used to it. Also you have to make sure when you move characters to place them last and click on them.

I really like some of the these ideas. I had completely forgotten that Rugged Re-roll allows me to split the party which is super useful but as the elevated maps I've got planned mean that the players should still be able to see each other despite the elevation I'd like to keep them on the same page. Using the 'wings' icon and adding +X for the given level I think will be super useful. I also hand-draw my maps and then bring them into Roll20 so can use @metroknight's idea of using different textures for different levels is another good idea. I might try colour coding them in some way that makes sense for the game world and possible use the coloured markers to link characters to levels.