The question is so general which makes it trivial to provide a specific answer. For example, Neural Network has been widely used for years, while it is still being enhanced (for example: Convolutional NN). Among most recent image classification approaches, sparse representation has recently opened a new demanding research area. The following paper is the latest one:
G. Shenghua, I. W. Tsang, M. Yi, "Learning Category-Specific Dictionary and Shared Dictionary for Fine-Grained Image Categorization,", IEEE Transaction on Image Processing, vol.23, no.2, pp.623,634, Feb. 2014
I think classification based on sparse representation is an easier choice for proposing innovations and enhancements, compared to NN and KSVM which are somehow saturated.