Having asked the question about research I've seen this elcomm report from 2009.
A negative for FRESH CHOICE FOR LONDON:4.1.2.
Participants liked having logos on the ballot papers. Logos helped participants identify parties easily. Some participants said that they used the logos to help them find the party they wanted to vote for.
Candidates who did not have logos on the ballot paper were seen as inferior. Independent candidates are not permitted to use a logo on the ballot paper. Participants saw these candidates as being “inferior”, and said they would be unlikely to vote for them as they didn’t seem “official enough”.
Having the candidates address on ballot papers was disliked. ...
If parties were listed alphabetically on ballot papers, this highlighted inconsistencies in party names
The position of a particular party on ballot papers which list parties alphabetically can vary between elections, depending on the name/description used (a political party may register up to 12 party descriptions, and may then use any one of these descriptions or the registered party name on the ballot paper). This resulted in participants taking longer to locate their chosen party if it was not listed in the order they would expect.4.2.5.
Party names are important in helping people find their choice, but are sometimes hard to find. Party names were not always instantly recognisable or prominent. The majority of participants said they identify their choice by party name or logo first. In particular this affected new voters who were not as familiar with party logos. They had to read the ballot paper closely to identify their choice
Party descriptions were disliked by many voters.
Participants did not notice or comment on the party descriptions until they were pointed out. They did not affect the results of the actual voting task. ... Most participants did not like them. ... Some participants thought they were very sloganised and inappropriate, and there was also comment on the practicality of fitting them on the ballot paper: ... Overall, even though there were a few mildly positive comments, the amount of strong negatives far outweighed these.
Expanded party descriptions make the ballot more difficult to read. Most participants were of the feeling that ‘less is more’ when it comes to the amount of text on the ballot. As a result of this, most thought party descriptions must be kept to a minimum if allowed at all.5. Conclusion
The main positive findings include:
Logos on the ballot paper meant participants could easily identify their party/candidate.
A clear visual indicator of where to cast the vote is helpful.