To a normal user (I.e. you aren't a Pandoc contributor or filter author) the AST is an implementation detail which you don't interact with. The normal user experience is pandoc -f markdown -t html`, i.e. you input a document in one markup format and get (a file) in anotheir markup format (possibly zipped together with sundry other files) as output, without any intermediate file or files. There is no point in creating a false impression that there always must be an intermediate file. In fact that may scare off potential normal users. To them the thing which sets pandoc apart from other light markup processors is that it supports conversion back and forth between multiple markup formats, and the logo should emphasize that. The logo needs to be intelligible and meaningful to the less geeky users which hopefully are in majority.
/bpj