Sorry i didn't answer all your questions before. I had to leave for school the second i typed that message.
Should i make some traps avoidable?, you know like some place where the trap doesn't affect
Ehh, You can do so, Just make sure that the course is still difficult for players.
How do i make a block or object spawn in a specific Area when a button is pressed? (for the creeper trap).
Make a point_template entity. Insert the name if what ever you want to spawn (name the object if it's not already) into the entity. Then you should be able to make the object spawn using a button. Click the Outputs tab and from there you can select the object. (Sorry about the brief instructions on this one. if you cant figure it out, Use this guide:http://www.youtube.com/watch?v=orlYUqoy-zg&feature=player_detailpage
I know notch doesn't like it when people take his minecraft textures but does anyone know where i could get more?
If you own Minecraft yourself, You already have all the skins, They're just hidden somewhere in a folder. Google it to find out where.
-edit
If you have any other questions, Feel free to contact me via steam/forum.
Steam name is calebcounterstrike