SetDirectory[NotebookDirectory[]]

CharFiles=FileNames["*.Bmp"];

nChars=Length[CharFiles]

chars = Import[#]& /@ CharFiles;

Length[chars]

Manipulate[chars[[k]],{k,1,nChars,1}]

ImageDimensions[chars[[1]]]

c=ImageCollage[chars[[1;;400]]]

Export["../c.png",c]