(seemingly a 'guest', not a member, so I cannot send this message privately to you?)
I discovered (and was 'hooked' by) wargaming *and* the use of 18th C. Imagi-Nations almost 40 years ago in C. Grant's 'The War Game' and I'm still deeply interested in the topic: http://wargamesfactory.lefora.com/2011/06/21/imagi-nations/#post0
Thus I noticed your posts about the 'United Provinces of Erin' in the 'Imagi-Nations: learn me' thread on the WF Forum while Googling for 'Imagi-Nations'.
Of all the intervenants you looked as the most motivated, already discussing the possible flags and uniforms of your 'creation'!
Is your project still active?
Do you know of the 'Emperor vs Elector' collective blog http://emperor-elector.blogspot.com/, the tribune of the 'League of Lace Wars Imagi-Nations' ? If browsing the 80-some individual blogs associated to it, you'll see how bewildering is the diversity of approaches, from 'novelization' of the picaresque adventures of a few characters to campaigns of continental scale.
About your flags and uniforms (totally unsolicited comments!):
- Flags: 'national flags' were practically unknown by the 18th C., the very concept appeared with the 'nations' born from the American and chiefly French Revolutions; at most there were 'identification jacks' used at sea to display the nationality of ships. The only noteworthy exception was the British 'Union Jack' used as the 'King's Colour' by infantry (but NOT the cavalry, so it was not yet a 'national' flag); probably because there was a recent 'Union' to 'hammer in the heads'? Then, since the 'United Provinces of Erin' are clearly born, like the USA, of what was at the same time a war of independence and a political revolution, the new state may well have a 'flag'; yet remember that the 'Stars & Stripes' was not used by the US army before 1835!
Actually during the 18th C. the 'nationality' of a military unit was indicated by the *pattern* of its flags, with generally different patterns for the infantry and cavalry; for instance in France infantry had flags with a white cross, cavalry standards or guidons with Louis XIV's 'Sun' on one side. Infantry regiments generally had two flags, one King's / Lieb / Colonel and one 'regimental' showing the facing color (initially the lining of the coat, visible at the cuffs, lapels, collar, turn-backs..) characteristic of the unit.
Thus your project of flag could be the 'State' flag of the infantry, while the whole Irish Wolf design (but with the motto in Gaelic, not hatred English!) could be device of the 'State' side of the cavalry flags.
Regarding the infantry flag, they were square, not rectangular, by then: not a problem if each of the 4 'components' is itself a square. Now, Ireland was traditionally divided in '4+1' (A + Tara) so the County of Meath can have its 'arms' appearing as an 'inescutcheon en surtout' http://en.wikipedia.org/wiki/Escutcheon_(heraldry)#Inescutcheon over the center of the flag? The corresponding colors don't appear on your post, but could provide the bases for the uniform of the Consular / Presidential Guard?
-Uniforms: a good and seducive idea to use the heraldic colors of the Provinces for the uniforms, but I'd restrict it to the Cavalry (and perhaps the 'Parliament Guard' of each province?): infantry was generally less colorful and, being the majority of the army, dressed with cheaper cloth bought in bulk quantities.
Thus 'normal' infantry would be in green coat, with perhaps the 'facing color' (often appearing also on the 'small clothes': waistcoat, breeches, stockings) indicating the Province of origin-red, blue, white, yellow.
Another characteristic was the 'metal' of the button (pewter / silver or brass / gold) reflected on the tape / lace edging the tricorne and often the buttonholes: white or yellow. For the infantry I'd give 'silver' to the 'line' and 'gold' to the 'Guard'.
For the cavalry, the 4 Provinces would provide units in yellow coat / red facings, blue coat / yellow facings, white coat / black facings, green coat / yellow facings, with 'gold' for Horse (Cuirassiers) [rectangular standard] and 'silver' for Dragoons [bilobed / swallowtail guidon]? Alternatively Dragoons (initially mounted infantry) can be all in green coat with facings as the infantry of same origin?
Do you have a blog? The best, most reader-friendly medium to share your project. On the TMP and Yahoo groups, illustrations (of limited size and resolution) are separated from text and practically deprived of captions. On forums, illustrations can be inserted in the text, but their size and resolution are limited (they are not 'clickable' to a larger version); and chiefly, your posts are scattered and 'lost' among a multitude of other peoples' ones, without the possibility to 'label / tag' them for easy sorting out and retrieval. While blogging is free, easy (even a dinosaur from the age of mechanical typewriters such as me can manage), everything posted can be edited later, you post at your own pace... Forums are great for exchanging informations and advices, and to post 'flashnews' linked to the relevant post on your own, project-devoted blog. And having to write down your ideas, plans, progress reports... in a 'publishable ' form greatly help to have them clear and straight.