open source     > level 1, order 1, name 'd:/Ctx-Beta/tex/texmf-context/tex/context/base/mkiv/cont-yes.mkiv'
system          > 
system          > ConTeXt  ver: 2019.04.16 08:54 MKIV beta  fmt: 2019.4.24  int: english/english
system          > 
system          > 'cont-new.mkiv' loaded
open source     > level 2, order 2, name 'd:/Ctx-Beta/tex/texmf-context/tex/context/base/mkiv/cont-new.mkiv'
system          > beware: some patches loaded from cont-new.mkiv
close source    > level 2, order 2, name 'd:/Ctx-Beta/tex/texmf-context/tex/context/base/mkiv/cont-new.mkiv'

system          > jobfiles > using path: d:\\Lukas\\ConTeXt\\Styles
system          > files > jobname 't', input 'D:\\Lukas\\Jobs\\_Px\\Present\\Px-2019\\_\\t.mkiv', result 't'
fonts           > latin modern fonts are not preloaded
languages       > language 'en' is active
open source     > level 2, order 3, name 'D://Lukas/Jobs/_Px/Present/Px-2019/_/t.mkiv'
fonts           > preloading latin modern fonts (second stage)
fonts           > 'fallback modern-designsize rm 12pt' is loaded
metapost        > initializing instance 'metafun:1' using format 'metafun' and method 'default'
metapost        > loading 'metafun' as 'd:/Ctx-Beta/tex/texmf-context/metapost/context/base/mpiv/metafun.mpiv' using method 'default'
metapost        > initializing number mode 'scaled'

tex error       > mp error on line 1 in file D://Lukas/Jobs/_Px/Present/Px-2019/_/t.mkiv:

>> picture
! Isolated expression.
<to be read again>
;
<*>  externalfigure "hacker.png";
;
I couldn't find an `=' or `:=' after the
expression that is shown above this error message,
so I guess I'll just ignore it and carry on.

[1]

 1 >>  \setupbackgrounds[page][background={Bkg}]
 2     
 3     \defineoverlay[Bkg][\useMPgraphic{Bkg}]
 4     
 5     \startuseMPgraphic{Bkg}
 6       externalfigure "hacker.png";
 7     \stopuseMPgraphic
 8     
 9     \starttext
10       Ahoj
11     \stoptext