Hello Heather
I think your eye for composition and composition is great and wish I'd taken some of your photographs myself. If entering into the stock photography market (and there's absolutely no reason why you shouldn't) there are two bits of advice I can give you.
First, nature-based imagery can be a fairly specialised area. Therefore, it may be worth considering placing some of work of this type with the higher-priced stock agencies (
www.sciencephotolibrary.com is the first one that comes to mind). On these sites you'll sell royalty-free images at a much higher price per download than you would on the microstock sites and with images of this type you're going to be catering to a rather limited audience. Whereas, pictures of children are likely to do well on microstock. For example, 'Friends forever' is good subject matter for general stock (but take the lettering of and consider taking the sepia effect off for some libraries).
Secondly, you will get images rejected and these rejections will be quite frequent with your first batches of submissions. Don't be disheartened. We all go through this. I can see evidence of noise/artifacts on some of the images on your website which will lead to images being rejected at most photolibraries. Just keep going and treat the rejections as part of your learning curve. You will learn much faster this way and by doing what you're doing here -- showing images and asking for advice.
I hope the above helps in some way and look forward to seeing your images on the stock libraries soon.