Just to be clear I've merged the two and upped the rez.
First of all, your plane stand should meet your terminal, as planes taxi upto the terminal then passengers get on.
Although yours being a small airport it wouldn't have bridges and people would walk from the terminal up to the aircraft.
Next moved the planes a bit, orange plane represents the wingspan of a taxiing plane which needs to be able to get past other big planes already sitting there.
I've added proper taxiway lines in, these should be in yellow, not white and while not very neat, show pretty much how they should be.
For your helipads you have a few choices of markings that I haven't put on. The first you need to decide if this airport has "dedicated helipads", which if so the place you have for them is a bit odd so I would suggest you don't.
If you do you have a few choices.
First being the setup I had on Bastion:
http://i.imgur.com/g7Jeh.jpg
Next is just a line that stops as I have pretty much done, which is what jets also have:
http://i.imgur.com/6TUz8.jpg
The next is a horizontal line to show where the chopper should stop:
http://i.imgur.com/xj8ky.jpg
But I would suggest just having a normal taxiway line, with no other indicator its where the helis are, and pilots will know where to come back to reload from where they took off, and not having any "H" on the ground or anything like that
Lastly you should probably add some direction numbers on the runways, although not critical, didn't have them on bastion as it didn't in r/l, would be good. The rest of your runway markings I think the size/scale might be a bit off but your modeller can deal with that
