ENH: Merge T1w images without biasing to first image
ENH: Merge T1w images without biasing to first image

oesteban/preprocessing-workflow,oesteban/preprocessing-workflow,poldracklab/fmriprep,oesteban/fmriprep,poldracklab/preprocessing-workflow,poldracklab/fmriprep,poldracklab/preprocessing-workflow,oesteban/fmriprep,poldracklab/fmriprep,oesteban/fmriprep