Not going angry level critic this time...
For your first map ever, not bad at all. Plain graphic design doesn't bother me at all.
The layout is actually quite well done, you have a tunnel that is mutual for many good LX levels.
Just add more stuff in there so playing would be a tad more diverse.
Also the black room that separates the rooms is a good thing to have. Perhaps add some destroyable platforms there?
The right side of the map is completely unnecessary, there's just a lot room for no purpose. I would simply delete it.
The aeroplane part is badly designed, but with a few changes it would turn out a whole lot better.
* Create an engineering room, add there some scheisse and especially a windshield that should be dirt.
* All the seats should not be solid nor dirt, increasing the gameplay.
ALL the boxes in that certain room should be dirt.
From the sauna there should be a path below -> adds a bit more dimension to the gameplay.
And what else? That cactus looks a bit lonely, design more stuff.
I did a few changes myself, didn't bother to design anything detailed since it's your level after all.
I'm not going to list all the little changes I made as you, being the levelmaker, should spot them right away and perhaps even get some ideas. Happy to be of service.
Link to the image:
http://img412.imageshack.us/img412/499/simplehouse.png