Pwnful - Excellent levels! I remember when I purchased the game, and believe me, mine were far worse than that.
Anyway, here are a few tips - These are really my opinions, people like different things. Also, I am ONLY trying to help you, please don't take offence to anything, if you might.
- Connections - Take a lot of time to make sure that all of the static objects "Connect" well. That is, they look nice together, and look like they "Fit".
- Multiple Solutions!!! - A excellent level is not one that is only solved one way. When designing your levels, be extremely open to all possible solutions, and how they would work on the level.
- Simple concept, but really has a lot of different solutions.
- Simplicity - Remember, these are only my Opinions, really. People may like different things. In most cases, a simple "Looking" level is the best. You really don't want 3/4 of the map covered in Static. BE AWARE - Sometimes this is necessary, like with the level above. I'm not saying you cannot do this, in any way.
- Dodge And Run, but slightly simpler, and more "Connected".
- Default Sizes - Try to not use the default sizes, be them Goals, or anything. This isn't a requirement, but it shows time, and effort.
Remember, that level making is a skill, and will develop by creating levels, playing levels, or even just thinking about them!