[squid-users] "unknown request" when configured to display custom logo

[reqman]

squid 3.5.19 on FreeBSD 10.3. The system has a LAN and WAN interface,
both in private address spaces. System's name is my.host.local,
listening on LAN at 192.168.0.1:3128. The system is not configured to
listen on localhost.

I am trying to replace the squid logo (SN.png) with the logo of my
agency. To do so:
1) I've copied mylogo.png to /usr/local/etc/squid/icons, alongside
SN.png. Same permissions for both files, same ownership:

 # ls -laF /usr/local/etc/squid/icons/
total 36
drwxr-xr-x  3 root  wheel    512 Jun 22 12:53 ./
drwxr-xr-x  4 root  squid    512 Jun 22 12:54 ../
-rw-r--r--  1 root  wheel  12716 May 19 16:15 SN.png
-rw-r--r--  1 root  wheel   7863 Jun 22 12:08 mylogo.png
drwxr-xr-x  2 root  wheel   1536 May 27 14:17 silk/

2) I've edited /usr/local/etc/squid/errorpage.css and replaced
/squid-internal-static/icons/SN.png with
/squid-internal-static/icons/mylogo.png

Details (filesize etc) of mylogo.png:

#file mylogo.png
mylogo.png: PNG image data, 82 x 72, 8-bit/color RGBA, non-interlaced

I've made both a squid -k reconfigure as well as a service squid
restart to make sure that the change propagates through. The problem
is that even though SN.png shows up just fine everywhere, the logo I
have created does not. The following errors appear when browsing FTP
sites (whereas the logo always appears) or when an HTTP error page has
to be displayed:

2016/06/22 12:57:38 kid1| internalStart: unknown request:
GET /squid-internal-static/icons/mylogo.png HTTP/1.1
Accept: */*
Referer: http://moystakas.gr/
Accept-Language: el
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1;
Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR
3.0.4506.2152; .NET CLR 3.5.30729)
Accept-Encoding: gzip, deflate
Proxy-Connection: Keep-Alive
Host: moystakas.gr

On access.log:

1466589376.848      1 192.168.0.209 TCP_MISS/404 5632 GET
http://my.host.local:3128/squid-internal-static/icons/mylogo.png -
HIER_NONE/- text/html

BR,


Michael.-