Newtype published a series of six novels adapting the storyline of the anime.  Each novel featured black and white drawings scattered throughout.  Some of the cover images are available in other artbooks, but the black and white drawings are (to my knowledge) not.  Rare stuff here, folks.  Allen-centric images only, but if you really, really beg, I might scan some images of other characters.
Cover of Novel 1 Amano (Hey, close enough) from Novel 1
Cover of Novel 2 Hitomi, Merle & Allen from Novel 2
Kissing Millerna's Hand from Novel 2 Hitomi, Merle & Allen Again from Novel 2
Cover of Novel 3 The Operation from Novel 3
With Chid from Novel 3 With Marlene from Novel 3
Cover of Novel 4 More Marlene from Novel 4
Kneeling before the Astons from Novel 4 Still More Marlene from Novel 4
Watching Dad Hit on Hitomi's Grandma from Novel 4 Kissing Hitomi from Novel 5
Not Kissing Hitomi from Novel 6
Select shots of Allen from both the shounen version of the manga and the shoujo version.  The shounen version has been translated since I first started this page and should be available wherever you get your manga fix.  To date, the shoujo version has not been translated and likely never will be.
SHOUNEN VERSION
1.  The second image of Allen in the manga.
2.  Still the consumate swordsman -- In a fight with Dilandau.  Dilandau fans should thank me not showing his/her/its full image.  
3.  The cover of the second volume of the manga.  Yep, the blue-haired guy is supposed to be Van.
4.  A scene between Allen and Millerna(!).  Why can't he be that brusque with her in the series?
5.  In some weird armor whose purpose I can't discern.
6.  Lecturing Van about something.  At least some things haven't changed.
7.  Apparently, another thing that hasn't changed is young Allen's penchant for playing with flowers, this time with young Millerna.
8.  Allen and Hitomi live out a bondage fantasy.  Actually, it's Allen right before being sent in front of a firing squad(!).
9.  My favorite picture in the five volumes that I have - manga Allen and Van cosplay as their series selves.
SHOUJO VERSION
1. The image on the back on the second volume.  Umm, fuzzy sweater.  You just want to rub your hands all over him.  Uh, it.
2. The first group shot.  A big improvement over the shounen version if you ask me.
3.  This must be what the covers of Asturian romance novels look like.
4.  It's official!  In all Escaverses, Allen kicks Van-butt in swordfights.
5.  Another group shot, this time in civilian outfits.  Civilian outfits from the 1980's...
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