The most compact ImageMagick distribution is the non-installed static version of ImageMagick. It requires the least number of dependent files.To reduce footprint you can remove any utility you won't use (e.g. display, composite, etc) or you can remove any image coder you won't use (e.g. miff, avs, etc).
There is a build option, UseEmbeddableMagick, which loads configuration information internally so ImageMagick won't need any external configuration files but it has reduced functionality (you can't specify delegates, for example).