How do I apply patch sized features to larger images?
The options are various.

If you want a naive and easy workaround simply resize your image (shrink it) and trust that the interpolation would preserve information.

If not, you might want to use Gaussian Pyramids or Spatial Pyramid Match Kernels:

http://www.ifp.illinois.edu/~jyang29/papers/CVPR09-ScSPM.pdf
http://www.vision.caltech.edu/Image_Datasets/Caltech101/cvpr06b_lana.pdf

Other options are a bit untidy. For example, you might take overlapping samples from it, apply some sort of feature extraction and if those features are still big for you, apply a PCA or LDA for dimensionality reduction. (There are more clever sampling strategies such as farthest point sampling : http://webee.technion.ac.il/people/zeevi/papers/17-00623193.pdf

Also taking a look at the covariance matrices might provide you relevant information. Why don't you also check:

http://static.googleusercontent.com/external_content/untrusted_dlcp/research.google.com/en/us/pubs/archive/36416.pdf

Cheers,