Another way, simpler but maybe less flexible is to add this to the YAML:
title: |
  ![ ](WGLogo.png){width=1in}  
  Your title here


On Thursday, 24 December 2020 at 21:35:19 UTC+2 the.so...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:

> I'm not a LaTeX expert, but I recently used this excerpted bit in a 
> metadata file, and it worked for me.  Your mileage may vary.
>
> ```
> header-includes: |
>   \usepackage{graphicx}
>   \usepackage{titling}
>   \pretitle{\begin{center}
>     \includegraphics[height=1.25in]{source/full-logo.png}\Huge\vskip 5em}
>   \posttitle{\vfill \color{NavyBlue} \LARGE Long Title of Project
>              \par \large PROJECT \par \normalsize Project Agreement No: 
> XXXX \par \end{center}}
> ```
>
>
> On Friday, 25 December, 2020 at 12:05:33 am UTC+5:30 gnpan wrote:
>
>> Hmm, I don't use Makefile so can't be sure what goes wrong - I put all 
>> the fontsize, mainfont, geometry, papersize, etc. in the YAML. Try 
>> something simple first:
>> Create a test.md file with the following content (or use the attachment):
>> ---
>> date: 24 December 2020
>> header-includes: 
>>   - \usepackage{wallpaper}
>>   - \addtolength{\wpYoffset}{12cm} 
>>   - \ThisCenterWallPaper{1}{WGLogo.png}
>> ---
>>
>> # Your title
>>
>> Your text. 
>>
>> Then run this command:
>> pandoc --pdf-engine xelatex -o test.pdf test.md
>>
>> That should work and you can take it on from there. 
>> On Thursday, 24 December 2020 at 19:54:28 UTC+2 LRP wrote:
>>
>>> Oops. I forgot to delete two lines in my YAML  file.
>>>
>>> error message now reads:
>>>
>>> Error producing PDF.
>>> ! LaTeX Error: Can be used only in preamble.
>>>
>>> See the LaTeX manual or LaTeX Companion for explanation.
>>> Type  H <return>  for immediate help.
>>> ...                                             
>>>                                                  
>>> l.65 \usepackage
>>>
>>> Here's YAML file:
>>>
>>> ---
>>> ...
>>> date: December 23, 2020
>>> header-includes:
>>>    - \usepackage{wallpaper}
>>>    - \ThisCenterWallPaper{1}{WGLogo.png}
>>> --
>>>
>>> Here's -how I call pandoc in Makefile:
>>>        pandoc \
>>>                 --top-level-division=chapter  \
>>>                 --variable mainfont="DejaVu Sans" \
>>>                 --variable monofont="DejaVu Sans Mono" \
>>>                 --variable fontsize=11pt \
>>>                 --variable geometry:"top=1in, bottom=2in, left=1in, 
>>> right=1in" \
>>>                 --variable geometry:a4paper \
>>>                 --table-of-contents \
>>>                 --number-sections \
>>>                 -f markdown  $< \
>>>                 --pdf-engine=pdflatex \
>>>                 -o $@
>>>
>>> Thanks again,
>>>
>>> LRP
>>>
>>>
>>>
>>>
>>>
>>> On Thu, Dec 24, 2020, at 12:33 PM, Lloyd R. prentice wrote:
>>>
>>> Thanks. But I get this feedback:
>>>
>>> [WARNING] Could not fetch resource 'WritersglenLogo_Color.png': 
>>> replacing image with description
>>> [WARNING] Could not fetch resource 'WritersglenLogo_Color.png': 
>>> replacing image with description
>>> Error producing PDF.
>>> ! Package pdftex.def Error: File 
>>> `WritersglenLogo\T1\textunderscoreColor.png' n
>>> ot found: using draft setting.
>>>
>>> See the pdftex.def package documentation for explanation.
>>> Type  H <return>  for immediate help.
>>>
>>> Here's m YAML declaration:
>>> ---
>>> ...
>>> date: December 23, 2020
>>> header-includes:
>>>    - \usepackage{wallpaper}
>>>    - \ThisCenterWallPaper{1}{WGLogo.png}
>>> ---
>>>
>>> And here's my source directory:
>>>
>>> -rw-r--r-- 1 lloyd lloyd 25516 Aug  1 00:31 WGLogo.png
>>> -rw-r--r-- 1 lloyd lloyd   871 Dec 24 12:23 Writersglen.md
>>>
>>> LRP
>>>
>>> On Thu, Dec 24, 2020, at 9:43 AM, gnpan wrote:
>>>
>>> You could use the wallpaper package (
>>> https://ftp.cc.uoc.gr/mirrors/CTAN/macros/latex/contrib/wallpaper/wallpapermanual.pdf
>>> ).
>>> Put the following in your YAML block:
>>> header-includes: 
>>>   - \usepackage{wallpaper}
>>>   - \addtolength{\wpYoffset}{12cm} 
>>>   - \ThisCenterWallPaper{1}{logo.png}
>>>
>>> Change logo.png to whatever you logo is called (make sure it's in the 
>>> same folder as your txt file) and adjust the Y offset to a value that gets 
>>> the logo in the required position. You can also change the scale factor 
>>> {1}. 
>>> On Wednesday, 23 December 2020 at 23:38:58 UTC+2 LRP wrote:
>>>
>>> I'd like to center a logo before the title on my PDF title page.
>>>
>>> I found a recipe on the web using \usepackage{titling} in the metadata, 
>>> but it failed. Can some kind soul show me how?
>>>
>>> Many thanks,
>>>
>>> LRP
>>>
>>>
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>>>
>>>
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>>>
>>>
>>>

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