One possible cause of your screenshot could be that the variable "albumart.size" is not properly set (or set to value 0) in your code (see the frame of the albumart picture).
But I fear that foo_uie_trackinfo_mod doesn't have the $eval-function. I then recommend you to use htpc9 which was written especially for trackinfo_mod (and doesn't use $eval). Alternatively, you would have to replace all uses of $eval like $eval(a+b*c) with $sum(a,$mul(b,c)) which would be a bit of work...
Replacing the $eval functions with $add or $sub wasn't too much work and seemed to do the trick. Thanks again for your help. I've included the code for anyone else who would like to use htpc4 and doesn't want to have to change the code. As-is it is dependent on using folder.jpg for your album art and artist.jpg for your artist art.
// Name: HTPC4
// Version: 1.0
// ---
// Description: A fullscreen trackinfo_mod/track display config for foobar2000
// Author: ojdo
// Global
$puts(coverPath,$replace(%path%,%filename_ext%,folder.jpg))
$puts(artistPath,$replace(%path%,%filename_ext%,artist.jpg))
$puts(path.artistart,$get(artistPath))
$puts(path.albumart,$get(coverPath))
$puts(font.a,$font(Arial,16,,120-120-120))
$puts(font.b,$font(Arial,16,,255-255-255))
$puts(swap.time,10)
$puts(swap.number,2)
$puts(col.border,60-60-60)
$puts(albumart.size,450)
// Background
$drawrect(0,0,0,0,pencolor-null brushcolor-5-5-5)
// PerTrack
// Artist photo
$imageabs2(%_width%,$muldiv(%_width%,3,4),0,$div($sub($muldiv(%_width%,3,4),%_height%),2),%_width%,%_height%,0,0,$get(path.artistart),NOKEEPASPECT NOCACHE)
$if(%title%,
// Panel bg
$drawrect(16,$sub(%_height%,226),$sub(%_width%,32),210,pencolor-0-0-0 alpha-220)
// Title
$alignabs($add(90,$get(albumart.size)),$sub(%_height%,234),$sub(%_width%,$get(albumart.size),90,40),110,left,bottom)
'#LINEHEIGHT,44#'
$font(Calibri,40,,255-255-255)
$if2(%title%,Unknown Title)
'#LINEHEIGHT,59#'
// Artist
$alignabs($add(90,$get(albumart.size)),$sub(%_height%,125),$sub(%_width%,$get(albumart.size),90,40),40,left,bottom)
$font(Calibri,24,,255-255-255)
$if2(%artist%,Unknown Artist)
,
// Nothing to display
$alignrel(center,middle)
$font(Calibri,40,,255-255-255)
No track loaded
)
// Album art
$if($get(path.albumart),
$drawrect(58,$sub(%_height%,$get(albumart.size),62),$add($get(albumart.size),4),$add($get(albumart.size),4),pencolor-$get(col.border) brushcolor-null)
$imageabs2($get(albumart.size),$get(albumart.size),0,0,$get(albumart.size),$get(albumart.size),60,$sub(%_height%,$get(albumart.size),60),$get(path.albumart),NOKEEPASPECT)
)
// Pause overlay
$if(%ispaused%,$if($get(path.albumart),
$drawrect(60,$sub(%_height%,$get(albumart.size),60),$get(albumart.size),$get(albumart.size),pencolor-0-0-0 alpha-150)
$alignabs(60,$sub(%_height%,$get(albumart.size),60),$get(albumart.size),$get(albumart.size),center,middle)$font(Webdings,100,,255-255-255)';'
,
$alignabs(60,$sub(%_height%,150,60),$get(albumart.size),150,center,middle)$font(Webdings,100,,255-255-255)';'
))
// Rating
$ifgreater(%rating%,0,
$drawrect(60,$sub(%_height%,42),$muldiv(%rating%,$sub($muldiv(220,$get(albumart.size),400),4),5),7,pencolor-null brushcolor-255-128-0)
,)
$drawrect(58,$sub(%_height%,44),$muldiv(220,$get(albumart.size),400),11,pencolor-$get(col.border) brushcolor-null)
// Mood
$ifgreater(%mood%,0,
$drawrect($add(60,$muldiv(220,$get(albumart.size),400),30),$sub(%_height%,42),$muldiv(%mood%,$sun($sub($get(albumart.size),$muldiv(220,$get(albumart.size),400),26),4),3),7,pencolor-null brushcolor-0-255-0)
,)
$drawrect($add(58,$muldiv(220,$get(albumart.size),400),30),$sub(%_height%,44),$sub($get(albumart.size),$muldiv(220,$get(albumart.size),400),26),11,pencolor-$get(col.border) brushcolor-null)
// PerSecond
// Third line
$alignabs($add($get(albumart.size),90),$sub(%_height%,85),$sub(%_width%,$get(albumart.size),90,40),30,left,bottom)
$select($add($mod($div($right(%cwb_systemdatetime%,2),$get(swap.time)),$get(swap.number)),1),
// A
$get(font.a)
$if(%album%,$get(font.b)%album%$get(font.a))
$if(%date%, '('$get(font.b)%date%$get(font.a)')')
$if(%tracknumber%,',' Track $get(font.b)$num(%tracknumber%,1)$get(font.a)$if(%totaltracks%,'/'$get(font.b)$num(%totaltracks%,1)$get(font.a))$if(%disc%, '('CD $get(font.b)%disc%$get(font.a)')'))
,
// B
$if(%last_played%,$get(font.a)Bisher $get(font.b)$if2(%play_counter%,0)$get(font.a)mal gehört', 'zuletzt am $get(font.b)$substr(%last_played%,9,10). $select($substr(%last_played%,6,7),January,February,March,April,May,June,July,August,September,October,November,December) $substr(%last_played%,1,4)$get(font.a).,$get(font.a)Bisher noch $get(font.b)nie$get(font.a) gehört.)
)
// Progress bar
$puts(width,$muldiv(%_time_elapsed_seconds%,$sub(%_width%,$get(albumart.size),90,60,4),%_length_seconds%))
$ifgreater($get(width),0,$drawrect($add($get(albumart.size),92),$sub(%_height%,42),$get(width),7,pencolor-null brushcolor-$if($strstr(%cwb_playback_order%,Shuffle),128-0-255,0-128-255)),)
$drawrect($add($get(albumart.size),90),$sub(%_height%,44),$sub(%_width%,$get(albumart.size),90,60),11,pencolor-$get(col.border) brushcolor-null)
Edit: Changed to codebox to clean things up a bit (learn something new every day).